Patagonia Nano-Air® Light Vest was made to be worn for the entirety of your aerobic, start-stop mountain activities, so you’re never slowed down by having to change layers. Stretchy and breathable FullRange® insulation dumps excess heat when you’re working hard and keeps you warm when you’re not. Fit: Slim Fit Size: Medium Stretchy, Breathable and PFC-Free Fabric The 100% recycled polyester ripstop shell and lining fabric offer mechanical stretch, exceptional breathability and improved abrasion resistance, with a PFC-free DWR finish (durable water repellent coating that does not contain perfluorinated chemicals) to resist light moisture; the microtexture keeps fabric from sticking to the skin for versatile comfort •FullRange® Insulation 100% polyester (93% recycled) insulation delivers outstanding warmth, mechanical stretch and air permeability (35 CFM), allowing excess heat to move away from the body •Built for Mobility, Articulated patterning and strategically placed, low-profile quilting combined with stretchy fabric and insulation provide an exceptional range of motion for unhindered movement •Zipper with Garage at the chin for next-to-skin comfort •Pocket Details, Two handwarmer pockets and single chest pockets are zippered, low profile and low bulk to wear comfortably with a harness or a pack; self-stuffs into the chest pocket •Low-Bulk Design, Cleanly finished armholes and hem are low bulk and keep things simple