If you are an off-road runner, trail gaiters are an essential part of your gear. Their purpose is simple: to prevent sand, dirt, prickles, mud, and gravel from getting in your shoes and causing irritation. Also saves your socks and keeps them cleaner!  The gaiter height you needs depends on how much protection you want.  Shorter gaiters like these Razer Trail Gaiters are made for trail running and summer hiking. Best fit is for ankle diameter of 9-10 inches.