The BT Racer Sock is a mid length sock for your coldest runs, made with our heat generating Breath Thermo® technology, this lightweight sock boasts all the warmth you need without the bulk.
- Small - Women's US size 6 - 8.5
- Medium - Men's US size 6 - 8.5; Women's US size 8.5 - 10.5
- Large - Men's US size 9 - 11; Women's US size 11 - 13
- Extra Large - Men's US size 11.5 - 14