Rubber BEST QUALITY RUBBER AND NEOPRENE: These boots are made from the all natural top quality rubber. The 7MM neoprene is from the best you will find. WATERPROOF: Waterproof neoprene uppers and protective rubber overlays VERY COMFORTABLE AND WARM: 7MM Neoprene to keep you warm and comfortable DURABLE OUTSOLES: Durable rubber outsoles for solid traction REMOVABLE INSOLES: Removable insoles help cushion your feet. EASY ON AND OFF: Pull tabs for a easy on and off GREAT BOOTS FOR WOMEN: simply subtract 2 sizes from your women’s shoe size. So a women’s size 7 shoe is equivalent to a big kids’ size 5 shoe.