Fibre Disc C-Silicone Carbide Used for Marble, stones, concrete building materials, bronze, brass, and hard cast iron Inner Hole:RoundDepressedCross hole Grit range :#16,24,36,40,50,60,80,100,120,140,150,180,220,280,320,360,400Available in the following sizes:100mm X 16mm (4” x 5/8”)115mm X 22mm (4.5” x 7/8”)125mm X 22mm (5” x 7/8”)150mm X 22mm (6” x 7/8”)180mm X 22mm (7” x 7/8”)230mm X 22mm (9” x 7/8”)