Attention: buy more than the 5 pairs get 1 pair free ,10 pairs get 2 pair free..........(The same style) ! Unlike normal athletic socks, Gear Stamina Socks are designed with gradient compression, The perfect performance gear designed for any activity where your legs are pushed to the limit. Gear Stamina Socks are engineered with the latest arch to calf compression technology, offering a targeted foot to calf muscle support unseen on lesser quality socks.The results are a boost in circulation, delivering an enhanced oxygen blood flow keeping you going harder, for longer, and recovering faster. US Sizing Guide - Women S/M Women| Shoe 5-9 | Calf 9in - 13in L/XL Women| Shoe 8 - 13 | Calf 13in - 16in XXL Women| Shoe 10&UP | Calf 16in - 20in US Sizing Guide - Men S/M Men| Shoe 5 - 9 | Calf 9in - 13in L/XL Men| Shoe 9 - 13 | Calf 13in - 16in XXL Men| Shoe 11&UP | Calf 16in - 20in