Vibram FiveFingers TrekSport Pink/Black 41 Womens Shoes Natural and synthetic materials 4mm Vibram TC1 Perfromance Rubber Outsole - Offers excellent grip, traction and protection for a wide varietyactivities. Heel and Instep Hook and Loop Closures - Helps pull the upper tight round the contours of your feet so it feels like a second skin. Razor Siped Outsole - For added flexibility and slip resistance. Seamless 2mm Footbed Insole - stitching free, to reduce friction and improve comfort