Made with moisture moving yarns and a splash of merino to keep your feet warm and dry, these Hotronic Heat Socks Only XLP PFI 50 Surround Comfort are also built with soft – PFI 50, 10 – 15 mmHg graduated compression to promote circulation and increase muscle recovery speeds. The spare pair for your kit these are the Surround Comfort heat socks, with a Surround Heating Element enveloping the toes for warmth top and bottom, keeping you comfortable out there in the cold. The Classic heat sock provides heat only on the underside of the toes, the Surround goes that extra step further to give you top and bottom protection, the protection needed by people who feel the cold or struggle with circulation issues. Like a good ski sock these give you added shin protection padding, for the complete ski sock with the magic of surround comfort warmth to keep you out there in the cold doing what you love to do. Fewer defrost breaks, more runs, the spare pair you need to get through your multi-day stays on the slopes!