Climb comfortably in our lightest, most breathable fully insulated hoody. The Proton SL Hoody was previously the Proton Lightweight Hoody.The lightest, most breathable option in our Insulation Collection, the Proton SL Hoody takes the guesswork out of warming up on cold climbs and other high-output activities in cool conditions. The knit insulation holds its loft and shape—no matter how often you stuff it into the bottom of your pack. More importantly, it allows your body to breathe, so you’re not left a sweaty mess after you have to step on the gas to get through the crux. What's been updated: Updated with recycled Fortius™ fabric for improved durability, and chest pocket and design lines that align with the Proton Collection. Need a heavier option? Try the Proton Hoody .