When you need it all on your next Ultra, the Adv Skin 12 Running Vest gives you epic carrying capability. The choice of demanding endurance runners, the ADVANCED SKIN 12 Vest offers more personalization in both fit and function. An updated sensifit and closure system make this pack even more comfortable for your unique body shape, and the 12L volume offers enough space for longer endurance races. Stability/freedom of movement The construction uses stretch, breathable fabrics that conform to the body, and lightweight adjustments for fit and stability. The pack doesn't bounce but allows comfortable breathing. This innovative sternum strap construction allows you to adjust and connect your pack quickly, even on the fly. The elastic strap also allows easy breathing during intense activity. The components of this pack are easy to use, and offer different ways to adjust the fit and carry poles and accessories.The Sensifit construction offers a snug, precise, comfortable fit and balances the load front and back, so you can move more freely and faster. The integrated soft flasks make it easy to drink as soon as you feel thirsty, and stays balanced when you run, so you can push the limit and stay hydrated.