90% polyester, 10% spandex liners with cotton/spandex lining can be worn directly against the skin. Sock Liner cannot function as a stand-alone piece and must be used in combination with the Heated One-Touch Programmable 12V Pant Liner (sold separately). Heating panel on top of foot features safe infrared technology that generates immediate heat to penetrate the body for deep warmth. Elastic band on calf keeps socks in place. Woven label at top of Sock Liner.