TREX 6304 Performance One-Piece Ice Traction Device Performance One-Piece Ice Traction Device: delivers tenacious grip and stability on ice and snow in contoured 3D design.12 rugged, heat-treated carbon steel studs for tenacious grip and stabilityStretchable rubber constructionContoured // "step in" 3D design that easily wraps boots and shoes for a superior fitFlexible to -40°F (-40°C)S (5-7), M (7-9), L (9-11), XL (11-14), see size chart for all countries#6301 replacement studs sold separatelyErgodyne