Scientifically tested. Athlete approved. Zoot's Ultra 2.0 CRx Socks continue to top the charts as a favorite piece of gear by athletes all over the world. NEW - NanoGLIDE yarn knit into heel and toe reduces blistering and hot spots and keeps feet drier and more comfortable. Updated with graduated muscle-specific zones of compression to stabilize muscles, reduce damage during exercise, and improve performance. Keep your legs feeling fresh through training and racing with Zoot's Ultra 2.0 CRx Sock. See our Size Charts tab for circumferential sizing information.