Info: Choose Pure Pumice Stone, or a Combination One with a Brush
Probably the best way to keep your feet from building up thick layers of yellow or callused skin is to rub them with a natural pumice stone (which is formed from volcanic lava!) daily. You can choose here between just a hand-sized stone, or a two-in-one combination, with a stone on one side and a brush on the other, to whisk the flakes of skin away and stimulate circulation.
Natural Lava Pumice Foot Stone (current product varies slightly from the one shown in the first two photos): Semi-rectangular shape, about 2 or 3 inches across, by nearly 2 inches high, and about 1-1/2 inches deep. Drilled at an angle through the top and a side for a hanging rope. Clean the stone by soaking it in boiling water for several minutes.
Combination Pumice & Foot Brush, with Wood Handle: an oval-shaped wooden-handle/ platform with natural pumice on one side, and natural bristle brush on the other, does wonders for your dry and calloused feet. It is about 3-1/4 inches long, 2 inches across, and 1-3/4 inches deep, altogether.