Warrior Coxswain-U 100% Rubber Imported Rubber sole Rubber recover insole massages your underfoot to stimulate blood flow alleviating sore muscles and aiding in cramp prevention Super light weight IMEVA (injected foam) creates added comfort and flexibility Midsole floats incase the product goes overboard Mesh venting airs out your funk and the whole kit is machine washable with a non-marking sole