Shed Grams. Go Adventure. The trim-fit men's PROTON LT is Arc'teryx super-light, synthetically insulated hoody-jacket that's exceptionally breathable. It's designed to perform as a mid layer under a shell during cold ski days, and for wear as a comfortable outer during hiking or climbing trips. Fortius Air 40 outer fabric effectively balances wind- and- water-resistance with air permeability. Coreloft Continuous 65 insulation pads this jacket, providing consistent warmth. A No-Slip Zip prevents the front zipper from self-opening during activities. Dual hem adjusters stop cold drafts from working their way into your core. Arc'teryx also equipped this jacket with an insulated, helmet-compatible hood that adjusts for optimal protection. Insulated front pockets keep your hands warm and dual zippered chest pockets serve as storage sports for your phone and map.
Shed Grams. Go Adventure. The trim-fit men's PROTON LT is Arc'teryx super-light, synthetically insulated hoody-jacket that's exceptionally breathable. It's designed to perform as a mid layer under a shell during cold ski days, and for wear as a comfortable outer during hiking or climbing trips. Fortius Air 40 outer fabric effectively balances wind- and- water-resistance with air permeability. Coreloft Continuous 65 insulation pads this jacket, providing consistent warmth. A No-Slip Zip prevents the front zipper from self-opening during activities. Dual hem adjusters stop cold drafts from working their way into your core. Arc'teryx also equipped this jacket with an insulated, helmet-compatible hood that adjusts for optimal protection. Insulated front pockets keep your hands warm and dual zippered chest pockets serve as storage sports for your phone and map.
Shed Grams. Go Adventure. The trim-fit men's PROTON LT is Arc'teryx super-light, synthetically insulated hoody-jacket that's exceptionally breathable. It's designed to perform as a mid layer under a shell during cold ski days, and for wear as a comfortable outer during hiking or climbing trips. Fortius Air 40 outer fabric effectively balances wind- and- water-resistance with air permeability. Coreloft Continuous 65 insulation pads this jacket, providing consistent warmth. A No-Slip Zip prevents the front zipper from self-opening during activities. Dual hem adjusters stop cold drafts from working their way into your core. Arc'teryx also equipped this jacket with an insulated, helmet-compatible hood that adjusts for optimal protection. Insulated front pockets keep your hands warm and dual zippered chest pockets serve as storage sports for your phone and map.
Shed Grams. Go Adventure. The trim-fit men's PROTON LT is Arc'teryx super-light, synthetically insulated hoody-jacket that's exceptionally breathable. It's designed to perform as a mid layer under a shell during cold ski days, and for wear as a comfortable outer during hiking or climbing trips. Fortius Air 40 outer fabric effectively balances wind- and- water-resistance with air permeability. Coreloft Continuous 65 insulation pads this jacket, providing consistent warmth. A No-Slip Zip prevents the front zipper from self-opening during activities. Dual hem adjusters stop cold drafts from working their way into your core. Arc'teryx also equipped this jacket with an insulated, helmet-compatible hood that adjusts for optimal protection. Insulated front pockets keep your hands warm and dual zippered chest pockets serve as storage sports for your phone and map.
Last updated at 12/10/2025 23:49:31
originally posted on altitude-sports.com
I own and love the Arc'teryx Atom LT and was intrigued by how the more "breathable" Proton would fair. At first zip-up, the jacket is very similar with the close-to-body well-designed feeling that comes with Arc'teryx jackets. I love Patagonia but synthetically-insulated Arc'teryx jackets solidly beat the Nano Airs in fit and feel. I measure 5'7 and weigh 160lb with a fit build and the medium fits like a glove.BreathabilityWhen I got moving in cool to cold weather though, I immediately noticed the absence of cold air entering through the side-panels like in the Atom. Conversely, the more breathable fabric meant that I also felt that my chest stayed warm without storing the heat that normally builds up under the Atom. I tested this while walking at night and ... MoreI own and love the Arc'teryx Atom LT and was intrigued by how the more "breathable" Proton would fair. At first zip-up, the jacket is very similar with the close-to-body well-designed feeling that comes with Arc'teryx jackets. I love Patagonia but synthetically-insulated Arc'teryx jackets solidly beat the Nano Airs in fit and feel. I measure 5'7 and weigh 160lb with a fit build and the medium fits like a glove.BreathabilityWhen I got moving in cool to cold weather though, I immediately noticed the absence of cold air entering through the side-panels like in the Atom. Conversely, the more breathable fabric meant that I also felt that my chest stayed warm without storing the heat that normally builds up under the Atom. I tested this while walking at night and cycling at high speed in strong, cold headwinds. I did feel the wind going through a little more than in the Atom but my heat was kept close to body and constant, as opposed to building up in select areas and being evacuated through the side panels like in the Atom. I imagine that the trimmer climbing fit also helps with this.How to decideIf you're looking for a jacket that keeps you warm when you're hanging out, walking and sitting and going for relaxed walks, then the Atom probably will probably give you more of the warm and fuzzy feeling you need. I've worn the Atom on long winter bus rides and while backpacking around Europe in January and it was great for this. If however what you're seeking is a more constant core warmth throughout your top body without any residue warm air, go for the Proton. In this regard especially, it makes for a better mid-layer when combined with a hard shell.The performance of the design and the materials in this jacket impressed me on the same level as when I bought my first pro Gore-Tex shell and realized that I was never sweating, never touched by gusting wind, always dry and protected by only a thin membrane. The Proton is slick and very technical but you'll likely get used to it so fast that you'll forget the existence of anything else and consider it your default for any time spent outside between -10 and 8 degrees.If you understand the different uses for the Proton and Atom, the last thing to be sure of is the close-to-body fit, no lower than waist length, slightly longer than normal sleeves (it's a climbing jacket) and smaller zippers and zip pulls (meant for climbing equipment).
originally posted on altitude-sports.com
I wore this on all of my cold weather walks/hikes last winter. With just a motus zip neck as a base layer, I wear this between 0 and -20 (give or take 5 degrees for output level and wind conditions). It does an amazing job of keeping me comfortably warm, without ever letting me feel sweaty or clammy. The breathability is definitely up to the stated active tasks. While high winds do cut through a bit, I didn't find this to be as big of a temperature impact as some suggested. I haven't yet worn this under a shell layer, but anticipate it being very versatile as a mid with a wind/soft/hard shell. The fit is typical for arc'teryx, which means it's brilliant through the body and I wish it were a little longer. I'm relatively tall and slim at 6'2", 180, and wearing a ... MoreI wore this on all of my cold weather walks/hikes last winter. With just a motus zip neck as a base layer, I wear this between 0 and -20 (give or take 5 degrees for output level and wind conditions). It does an amazing job of keeping me comfortably warm, without ever letting me feel sweaty or clammy. The breathability is definitely up to the stated active tasks. While high winds do cut through a bit, I didn't find this to be as big of a temperature impact as some suggested. I haven't yet worn this under a shell layer, but anticipate it being very versatile as a mid with a wind/soft/hard shell. The fit is typical for arc'teryx, which means it's brilliant through the body and I wish it were a little longer. I'm relatively tall and slim at 6'2", 180, and wearing a medium. I think most people my size would wear a large, but I value the fit through the body over the length. I own this and the Proton FL. I prefer the pocket configuration on the FL. Otherwise they serve the exact same function at two different temperature ranges (I run warm and switch between 0 and 5, some might switch closer to 10, there's probably 5-15 degrees of overlap depending on layering).
originally posted on REI
Overall an excellent active use jacket. I had been wearing an Atom LT but found it did not breath well during activities like cross country skiing and snow shoeing so I would overheat. I went to the Proton LT and as advertised it breaths noticeably better than the Atom. It is not as wind proof as the Atom but better than my Patagonia Nano Air, which breaths better but has almost no wind protection. The Proton is a good compromise in breathability and weather protection. The shell fabric feels a bit softer than the Atom which makes the jacket wear more comfortably.
| Centre back length | 74.8cm/29.4in |
I own and love the Arc'teryx Atom LT and was intrigued by how the more "breathable" Proton would fair. At first zip-up, the jacket is very similar with the close-to-body well-designed feeling that comes with Arc'teryx jackets. I love Patagonia but synthetically-insulated Arc'teryx jackets solidly beat the Nano Airs in fit and feel. I measure 5'7 and weigh 160lb with a fit build and the medium fits like a glove.BreathabilityWhen I got moving in cool to cold weather though, I immediately noticed the absence of cold air entering through the side-panels like in the Atom. Conversely, the more breathable fabric meant that I also felt that my chest stayed warm without storing the heat that normally builds up under the Atom. I tested this while walking at night and ... MoreI own and love the Arc'teryx Atom LT and was intrigued by how the more "breathable" Proton would fair. At first zip-up, the jacket is very similar with the close-to-body well-designed feeling that comes with Arc'teryx jackets. I love Patagonia but synthetically-insulated Arc'teryx jackets solidly beat the Nano Airs in fit and feel. I measure 5'7 and weigh 160lb with a fit build and the medium fits like a glove.BreathabilityWhen I got moving in cool to cold weather though, I immediately noticed the absence of cold air entering through the side-panels like in the Atom. Conversely, the more breathable fabric meant that I also felt that my chest stayed warm without storing the heat that normally builds up under the Atom. I tested this while walking at night and cycling at high speed in strong, cold headwinds. I did feel the wind going through a little more than in the Atom but my heat was kept close to body and constant, as opposed to building up in select areas and being evacuated through the side panels like in the Atom. I imagine that the trimmer climbing fit also helps with this.How to decideIf you're looking for a jacket that keeps you warm when you're hanging out, walking and sitting and going for relaxed walks, then the Atom probably will probably give you more of the warm and fuzzy feeling you need. I've worn the Atom on long winter bus rides and while backpacking around Europe in January and it was great for this. If however what you're seeking is a more constant core warmth throughout your top body without any residue warm air, go for the Proton. In this regard especially, it makes for a better mid-layer when combined with a hard shell.The performance of the design and the materials in this jacket impressed me on the same level as when I bought my first pro Gore-Tex shell and realized that I was never sweating, never touched by gusting wind, always dry and protected by only a thin membrane. The Proton is slick and very technical but you'll likely get used to it so fast that you'll forget the existence of anything else and consider it your default for any time spent outside between -10 and 8 degrees.If you understand the different uses for the Proton and Atom, the last thing to be sure of is the close-to-body fit, no lower than waist length, slightly longer than normal sleeves (it's a climbing jacket) and smaller zippers and zip pulls (meant for climbing equipment).
I wore this on all of my cold weather walks/hikes last winter. With just a motus zip neck as a base layer, I wear this between 0 and -20 (give or take 5 degrees for output level and wind conditions). It does an amazing job of keeping me comfortably warm, without ever letting me feel sweaty or clammy. The breathability is definitely up to the stated active tasks. While high winds do cut through a bit, I didn't find this to be as big of a temperature impact as some suggested. I haven't yet worn this under a shell layer, but anticipate it being very versatile as a mid with a wind/soft/hard shell. The fit is typical for arc'teryx, which means it's brilliant through the body and I wish it were a little longer. I'm relatively tall and slim at 6'2", 180, and wearing a ... MoreI wore this on all of my cold weather walks/hikes last winter. With just a motus zip neck as a base layer, I wear this between 0 and -20 (give or take 5 degrees for output level and wind conditions). It does an amazing job of keeping me comfortably warm, without ever letting me feel sweaty or clammy. The breathability is definitely up to the stated active tasks. While high winds do cut through a bit, I didn't find this to be as big of a temperature impact as some suggested. I haven't yet worn this under a shell layer, but anticipate it being very versatile as a mid with a wind/soft/hard shell. The fit is typical for arc'teryx, which means it's brilliant through the body and I wish it were a little longer. I'm relatively tall and slim at 6'2", 180, and wearing a medium. I think most people my size would wear a large, but I value the fit through the body over the length. I own this and the Proton FL. I prefer the pocket configuration on the FL. Otherwise they serve the exact same function at two different temperature ranges (I run warm and switch between 0 and 5, some might switch closer to 10, there's probably 5-15 degrees of overlap depending on layering).
Overall an excellent active use jacket. I had been wearing an Atom LT but found it did not breath well during activities like cross country skiing and snow shoeing so I would overheat. I went to the Proton LT and as advertised it breaths noticeably better than the Atom. It is not as wind proof as the Atom but better than my Patagonia Nano Air, which breaths better but has almost no wind protection. The Proton is a good compromise in breathability and weather protection. The shell fabric feels a bit softer than the Atom which makes the jacket wear more comfortably.
I would say if you’re looking for a great mid layer that can keep the heat once you get going, this is a really good pick for you. I am 177 pounds and about 5’8. Typically I run a size medium. However, with the proton it does not run small but it has a more tighter architecture where it hugs your body. If you’re looking for a little more room I’d recommend going up to a large (which I personally went for) however if you want a more compact feel go with your regular sizing. In terms of durability I’ve used the jacket about 10 times mainly for snowboarding under my AK Burton Jacket and have had no problems. Once I get going the warmth really does not go away and this is at -20 temperatures. Overall a great build for my use.
This is by far my favorite product from Arc'teryx and covers a wide array of use-cases. The price may seem steep but it's well worth it. If you really look at the current product landscape, Arc'teryx is similarly priced compared to other performance brands.Fit (Men's Medium): Excellent Slim Fit (5'9", 165lb, 41" Chest, 31" Waist, Climber's Build)Pros:+ Unparalleled slim fit+ Excellent comfort and design (e.g. materials used for inner lining and cuffs is very intentional and function).+ Highly breathable, yet still warm in most scenarios+ Versatile (good static warmth in mild and cool weather, excellent outer layer during high-output activities in cold weather).+ Easy care (can pop in delicate cycle with cold water and tumble dry on low heat)Cons:- ... MoreThis is by far my favorite product from Arc'teryx and covers a wide array of use-cases. The price may seem steep but it's well worth it. If you really look at the current product landscape, Arc'teryx is similarly priced compared to other performance brands.Fit (Men's Medium): Excellent Slim Fit (5'9", 165lb, 41" Chest, 31" Waist, Climber's Build)Pros:+ Unparalleled slim fit+ Excellent comfort and design (e.g. materials used for inner lining and cuffs is very intentional and function).+ Highly breathable, yet still warm in most scenarios+ Versatile (good static warmth in mild and cool weather, excellent outer layer during high-output activities in cold weather).+ Easy care (can pop in delicate cycle with cold water and tumble dry on low heat)Cons:- Some might say price, but competitors aren't much cheaper in this product class- Can run small if you are used to standard fits- Face fabric can be somewhat delicate for activities like climbing, but is acceptable
I can't say enough good things about this jacket.I bought it because I'm a runner and I need something that'll keep me warm during the winter months.I've worn it in -8 (with windchill) so far, and it's kept me fantastically warm.The original plan was to wear this with a shell, but this jacket is so fantastic that I won't have to wear it until it's at least -20.I haven't even thrown a proper baselayer underneath it yet. I'm currently just wearing a long sleeve running shirt and a beanie on my head, and I'm super toasty.I used to wear a lightweight puffer with a Nike Windrunner coat on top of it, and that combo doesn't come close to what this jacket does.I love the insulated hood too. It helps to keep my cheeks and mouth warm.AND THIS JACKET BREATHES WELL ... MoreI can't say enough good things about this jacket.I bought it because I'm a runner and I need something that'll keep me warm during the winter months.I've worn it in -8 (with windchill) so far, and it's kept me fantastically warm.The original plan was to wear this with a shell, but this jacket is so fantastic that I won't have to wear it until it's at least -20.I haven't even thrown a proper baselayer underneath it yet. I'm currently just wearing a long sleeve running shirt and a beanie on my head, and I'm super toasty.I used to wear a lightweight puffer with a Nike Windrunner coat on top of it, and that combo doesn't come close to what this jacket does.I love the insulated hood too. It helps to keep my cheeks and mouth warm.AND THIS JACKET BREATHES WELL TOO!I'm always toasty but never worry about overheating.I'm pretty confident that I'll stick to just wearing a long sleeve running shirt underneath this until the temperature dips to -15 before I even contemplate putting on a proper baselayer.I'm guessing I'll have to wait for the temperature to dip to -20 (or even -25) before I use my shell.
This jacket holds a lot of promise, but I could only review it during the peak of summer. I took it out during the morning lows (before dawn) for heavy activity. It took me 15 minutes before I got too hot in the 60degF weather, but in that time it kept the chill off and was very breathable. In fact, it showed great breathability. During chilly summer nights, or late spring / early fall days, I'll often wear a flannel shirt or sweatshirt. I find these versatile options work well for me. With this hoodie, I expect to find a similar versatile range but for colder temps. With this synthetic option, I'll have the confidence for high activity in the cold. Some have mentioned that cold wind passes through the jacket - this is great! If you'd need a wind break, a light ... MoreThis jacket holds a lot of promise, but I could only review it during the peak of summer. I took it out during the morning lows (before dawn) for heavy activity. It took me 15 minutes before I got too hot in the 60degF weather, but in that time it kept the chill off and was very breathable. In fact, it showed great breathability. During chilly summer nights, or late spring / early fall days, I'll often wear a flannel shirt or sweatshirt. I find these versatile options work well for me. With this hoodie, I expect to find a similar versatile range but for colder temps. With this synthetic option, I'll have the confidence for high activity in the cold. Some have mentioned that cold wind passes through the jacket - this is great! If you'd need a wind break, a light shell (even summer rain jacket) would be the perfect match.The slim fit has high arm holes. While it makes for excellent arm articulation (torso section really doesn't ride up when you raise your arms), you'll want to wear similar slim-fit next-to-skin or other slim layers under the jacket.Hand pockets perfectly placed. With a backing backpack, I have 90% access with my hip belt on. Yet, they are low enough to comfortably use when wearing the jacket around town, without bulges around my tummy.I got a Large size. I'm 5' 11", 180 lbs with a 42in chest. The large is a touch wide through my shoulders, and the sleeves bunch very slightly. This is perfect, as I get the slim fit but still have room for under layers and length left in the sleeve when I'm active/ reaching. Someone a touch bigger than me would be fine in the Large.
The most critical aspect to staying warm in winter sports is to stay dry. This jacket breathes like no other I have ever owned. I have had several of the competitors breathable jackets as well as the Atom. This is a whole other product. After a year and a half of wear and washes, the outer layer of this jacket still beads water. This is not meant to be a rain jacket but I can stay dry in the drizzle until it begins to leak through the seams, which takes about 2 hours in the rain in the PNW. When sweating heavily, you wont realize how well this jacket breathes until you wear it under a shell. You will feel perfectly dry, not knowing how much you are sweating, to take off the shell and find the interior of the shell absolutely soaked with the moisture this jacket ... MoreThe most critical aspect to staying warm in winter sports is to stay dry. This jacket breathes like no other I have ever owned. I have had several of the competitors breathable jackets as well as the Atom. This is a whole other product. After a year and a half of wear and washes, the outer layer of this jacket still beads water. This is not meant to be a rain jacket but I can stay dry in the drizzle until it begins to leak through the seams, which takes about 2 hours in the rain in the PNW. When sweating heavily, you wont realize how well this jacket breathes until you wear it under a shell. You will feel perfectly dry, not knowing how much you are sweating, to take off the shell and find the interior of the shell absolutely soaked with the moisture this jacket moved away from your body (my my Beta SL Hybrid was dripping inside when I took it off from over this jacket). My only complaint is that the chest pocket material is not as insanely breathable as the rest of the jacket and sometimes condensation will dampen anything in that pocket. I cannot think of a more useful, bang for your buck, piece of outdoor equipment. The sizing is perfect, you can fit a light fleece underneath and it looks stylish enough to wear in the city, or fit a shell over it. It has better wind resistance than a fleece, but nothing like a pertex jacket. I would make sure to have a shell if you plan on using this in a very windy climate. Arcteryx products can be hit and miss, but this is by far the best jacket on the market and well worth the money.
This is my 3nd favorite Arc'teryx piece! After the Proton FL (1) and my 395A climbing harness (2). So may commenters complaining that they get cold in the LT at -0 degrees? LoL. They really want one jacket you can live in at 50 to -20? You know they make an AR, right? With thicker insulation, right? 120 for the AR, 80 for the LT? Or just layer a shell, (like Arc'teryx states) and you're good for most any bad weather. Reading these comments, I start to see why the Proton FL, (The most all around "California Climate" jacket ever made) seems to have been discontinued. These folks probably thought it would work from 70 to 10 degrees, with high output at 70 and resting at 10! It's really sad. The Proton line is really bomber. The fabric rarely snags, when in brush. My ... MoreThis is my 3nd favorite Arc'teryx piece! After the Proton FL (1) and my 395A climbing harness (2). So may commenters complaining that they get cold in the LT at -0 degrees? LoL. They really want one jacket you can live in at 50 to -20? You know they make an AR, right? With thicker insulation, right? 120 for the AR, 80 for the LT? Or just layer a shell, (like Arc'teryx states) and you're good for most any bad weather. Reading these comments, I start to see why the Proton FL, (The most all around "California Climate" jacket ever made) seems to have been discontinued. These folks probably thought it would work from 70 to 10 degrees, with high output at 70 and resting at 10! It's really sad. The Proton line is really bomber. The fabric rarely snags, when in brush. My Atom jackets snag on everything they touch. The Protons shed a light rain, like they're made for it. The atom line absorbs water like a sponge. I've been caught in a storm in the Atom LT and started to go hypothermic. near disaster. Shortly after I purchased the Proton LT, I don't use an Atom unless I am in my own house. The Proton LT is perfect for Fall through Spring. Then the FL comes out, perfect for late Spring through early Fall. Great for everything but extreme high output summer days like biking to running. I guess people need to do a little more research, than picking a cool color and logo placement.
I love this jacket. It's exactly what I was looking for in a cold weather jacket for hiking and easy outdoor activities, as well as casual wear. The insulation feels very warm and compact, and the jacket has a slim fit to it, which is good for me as a taller, thinner person (6'0, 150 lbs, size M). The hood is bigger, as it's designed to be able to use helmets with, but the draw string in the back is a nice feature to synch it up a bit tighter for a better fit without one. The length is good down past the hips and I am pleased with sleeve length and the tightened cuffs at the end for a snug fit. It fits very well underneath a rain shell, and the jacket itself does a good job of resisting some light rain/misting. Again, I love this jacket for what I bought it for. It ... MoreI love this jacket. It's exactly what I was looking for in a cold weather jacket for hiking and easy outdoor activities, as well as casual wear. The insulation feels very warm and compact, and the jacket has a slim fit to it, which is good for me as a taller, thinner person (6'0, 150 lbs, size M). The hood is bigger, as it's designed to be able to use helmets with, but the draw string in the back is a nice feature to synch it up a bit tighter for a better fit without one. The length is good down past the hips and I am pleased with sleeve length and the tightened cuffs at the end for a snug fit. It fits very well underneath a rain shell, and the jacket itself does a good job of resisting some light rain/misting. Again, I love this jacket for what I bought it for. It does what I need it to as a standalone layer on cold days (down to 32 F) and as a mid layer (below freezing).
| Centre back length | 74.8cm/29.4in |
