Stretchy, breathable synthetic mid-layer pants Layer up for a cold day on the mountain. Stay warm at base camp. The men's Burton [ak] Helium Stretch Insulated Pants are that extra layer that makes a difference on the coldest days. Stretchy and breathable, they're made for wearing under your shell pants or bibs, but they're so comfortable you'll prob wear them for a lot more things, too. Features: Low-bulk insulation adds warmth while staying breathable when you're working hard. Stretch fabric and waistband let you move easily without feeling restrictive. Zippered hand-warmer pockets and a back pocket add utility and keep choice items close. Bluesign® approved materials reduce impact on humans and the planet during manufacturing.