Mountain Lab heated socks provide warmth on demand, right where you need it. A low-profile heating element completely encircles the toes and forefoot area. The element is powered by a lightweight battery housed at the top of the cuff, where it won&';t interfere with tall boot cuffs. The socks use a 50% wool, 50% polyester blend for continuous warmth and comfort, even in damp conditions or when the socks are not powered on. Left and right markings on the socks help with easy identification. The Remote Control Heated Socks can be operated individually by using a button on the sock battery itself (located at the cuff of the sock) or together with use of the included remote control. The remote control allows the sock heat to be turned on or off, and the heat level to be adjusted between three intensity settings: Low, Medium and High. Heat Setting Temperature Duration Low 38-45AdegC // 100-113AdegF 8 Hours Medium 45-50AdegC // 113-122AdegF 5 Hours High 50-55AdegC // 113-122AdegF 2.5 Hours Sizing: SIZE US WOMEN SHOE SIZE US MEN SHOE SIZE SMALL 4-6 - MEDIUM 7-9 6-8 LARGE 10-12 9-11 X-LARGE - 12-14