Sanding blocks are 1/8" neoprene foam (mousepad) glued over 1x2 & 1x3 scrap pine, with 1/4" roundovers ( makes 3/8" roundover with padding. ) Use waterproof contact cement. The large block is sized for 1/4 of a standard sheet of sandpaper, and will also take half of a 1/3 sheet piece. Small block works well for details, inside horns, etc. The neoprene grips the sandpaper exceedingly well, wet or dry, and has just the right amount of 'give' for very fine sanding.