Quickly reshapes and resurfaces abrasive stones to like-new condition. A very hard and coarse silicon carbide stone with 4 different sized half-round grooves on one side measuring 1/16" (1.6 mm), 1/8" (3.2 mm), 3/16" (4.8 mm) and 1/4" (6.4 mm). Stone measures 3-1/2" x 1-1/2" x .56" .