GEHWOL Sponge for Hard Skin with double action coarse and fine pored mineral callus sponge. The coarser, white side is for removing stubborn callus, welts and corns from the feet. The finer, blue side is for hands, ankles, knees, etc. Dead skin cells are removed - the skin becomes tender and soft. A GEHWOL Foot Bath makes it easier to remove callus.