Anatomically knitted with high quality materials for a perfect fit; A unique blend of Merino Wool and Warm Reflector for optimal heat retention; Easy battery attachment with press studs; Cushioned reinforcement under the foot: maximum comfort, better heat circulation, toe and heel protection; Micro-aerated foot arch for good moisture release; Composition: 41% Polyamide, 20% Merino Wool, 13% Polypropylene, 13% Acrylic, 11% Polyamide Microfiber, 2% Lycra; S-Pack Bluetooth Battery keeps your feet warm for up to 8/16 hours; Batteries are equipped with Bluetooth technology, so you can control the heating of your socks from your smartphone; Pack includes two rechargeable batteries; USB charger included