This cap is amazing because it keeps out dust, cat hair, pollen, fungal spores, house dust and mites. But there's more. It works on bed bugs, too. Sadly, there were no color options, but black is sufficient. To improve visibility, I used my wife's gold glitter nail polish to highlight the tiny raised bump that indicates alignment. This bright spot helps in any lighting situation and speeds up the troublesome nuisance of constantly re-capping after switching lenses. Overall a solid product.

The cap for EF mount can be attached in one of the 3 positions: the flanges are symmetrical. Thus worse case scenario is a rotation by 120 degree, on average 60 degree. This is why it was so easy to put it on blindly, even while walking toward the next shot. Here the RF cap has asymmetrical flanges, and it fits in one position only. In worse case one needs a rotation by 360 degree, on average 180 degree. Worse still, the cap can wedge in the wrong position, get stuck half closed. This is a horrible design. I even started to use these Nikon Z Teflon caps for low end lenses, however Z-mount is 1mm bigger and they are a bit too lose. I am constantly looking for a 3rd party replacement for RF caps.

Spare lens caps are essential to have. I've never lost a front lens cap since I started using the metal screw-on type, but rear lens caps have a habit of getting stuck in an odd place when changing lenses in a rush, to get lost in camera bags.... I like to keep extras in my camera bag and in the truck just so I never have to put a lens away without a rear lens cap. Even if a put a lens in a zip lock bag, I'd still worry about what might be on the lens that would find its way into the rear of the lens.