Kalso Earth Women's Exer-Flip Thong Sandals Kalso Negative Heel Technology sets feet at a 3.7-degree incline to strengthen and tone muscles. Shock-absorbing, flexible footbed features anatomic arch support to keep you steady on your feet. Latex rubber outsole provides increased durability and traction as you walk. Polyurethane upper and upper lining, EVA insole, midsole, latex rubber outsole. Care: Spot clean with a damp cloth.