Yaktrax Run Traction Cleats were designed by athletes to allow users to continue trail running and training in winter. Run Traction Cleats attach over trail running shoes with a high-strength rubber foot frame that includes straps over the toe as well as over the top of the foot for additional security; the heal and side straps of the frame feature reflective material for safety. Yaktrax Run Cleats offer superior traction thanks to replaceable, 3mm carbide-steel spikes combined with a shaped-edge coil design of 1.4mm rust-resistant stainless steel coils so users can run with confidence on packed snow or ice. Multiple coil angles provide 360 degrees of traction on cold surfaces for stability in all directions. Yaktrax Run Traction Cleats have been tested in temperatures as low as -41 degrees Fahrenheit so they can be used in a variety of extreme environments. Yaktrax Run Traction Cleats come in four sizes to fit most shoes: Small (fits shoe size W6.5-10, M5-8.5); Medium (fits shoe size W10.5-12.5, M9-11); Large (fits shoe size W13-15, M11.5-13.5); X-Larger (fits shoe size W15.5+, M 14+). For oversized shoes or boots, Yaktrax recommends purchasing one size larger than your normal shoe size.