Using Seirus® exclusive modern fibers the Dynamax™ Skull Liner provides awesome warmth, wicking, and wind block in a thin, lightweight package. With Dynamax™, the feel is unreal. Seirus'® exclusive dual-density, micro denier hollow-core Thermax® material is warm enough to wear alone, but thin enough to layer under hats, helmets, or anything else.Recommended for: On-mountain cold weather adventures (skiing, snowboarding, hiking, fishing, etc), activities in high wind