Fibre Disc A-Aluminum OxideUsed for Iron, mild steel welding rods, cast iron, aluminum, non ferrous metals, polyester & wood. Inner Hole: Round Depressed Cross hole Grit range :# 16,24,36,40,50,60,80,100,120. Available 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”)