The Smartwool Run Zero Cushion Low Ankle Sock is built to disappear during a run instead of getting in the way. A Virtually Seamless(TM) toe cuts down on the friction that causes blisters, and an Achilles heel tab keeps the sock from sliding down into the shoe mile after mile. Zero Cushion keeps things minimal without sacrificing comfort, with mesh zones adding breathability right where feet run hottest. A 4 Degree(TM) elite fit system locks the whole sock into a dialed-in fit built for real training pace. What Our Gearhead(R) Experts Are Saying:"I ran a full marathon training block in these and never dealt with a single blister or had to stop and pull one up."