Here's what other sites are saying:
Ideal for cool-weather starts, slip the Seirus Thermax skull liner beneath your helmet or pack it as a minimalist beanie for light and fast adventures.
- REI refers to the men's version
For moisture-wicking comfort that keeps your head dry and warm, wear the Seirus Thermax Skull Liner under your helmet or hat.. . . Ultrathin Thermax for moisture-wicking warmth and dry comfort. Flat-seam construction for a smooth, comfortable fit. Lightweight skull cap for versatile wear alone or under a helmet or hat
Seirus Thermax Skull Liner is made with flat seam construction for comfortable fit. Thin, warm and comfortable.Warm, dry, wicking comfort.Thermax 4-way stretch polyester fabric.Layers under hats, fits under helmets.Reverses to solid black.Avg. wt. 1 oz.Import.