Professional grade threaded spikes provide easy spike customization and extend life of product. Quick-release buckle and strap system for easy on/off. 36 easily replaceable threaded steel spikes per pair placed under toe, heel and ball of foot. Molded rubber walls at toe, heel, and side provide secure fit. Combination of aggressive rubber lug and steel spike pattern provides traction on any surface. Includes 10 additional replacement spikes and 1 replacement buckle. (Sizing US: Men's: MD 7-9.5, LG 10-11.5, XL 12-13.5, XXL 14-15, Women's: MD 8-11, LG 11.5-12). Material: Synthetic, Rubber, Steel.