These are Smartwool's lowest cut performance socks, are the preferred style of sock by many for use with trail running shoes, and feature cushioning in the heel and ball of foot.  The x-patterned 4 Degree™ Elite Fit design hugs your foot and helps prevent blisters and hot spots by holding the sock in place and keeping it from shifting and bunching.  Mesh venting keeps you cool.  A great low cut training sock, and one of Smartwool's most popular socks.