Nike Solarsoft Thong 2 Grey Mens Sandals Rubber Rubber sole Synthetic Plastic UPPER: Soft, injected thermoplastic rubber. MIDSOLE: Soft, pliable Nike Solarsoft foam with grooves for airflow and drainage. OUTSOLE: Nike Solarsoft foam in a harder durometer for better durability and traction. Nike innovation used to create the most comfortable slipper you will ever wear.