Superfine Merino wool combined with ultrafine tekoPOLY(eVAPOR8?) fibers dry & evaporate moisture quickly, SIN3RGIfiber regulates your temperature * Anatomical fit - smooth, seamless & snug,Performs across a wide range of temperatures & conditions * Ultralight/Light/Medium* IMPAX Zoned Cushioning System for optimum comfort * Extremely durable, Lifetime tekoFITGuarantee