Gator Grit 2 Pack 3" x 21" 40 Grit Extra Coarse Bi-Directional Sanding Belt. These premium sanding belts are designed for heavy duty sanding and grinding of wood, metal, fiberglass and painted surfaces. The sanding belts are made with a resin bonding system that resists heat and humidity giving the sanding belt a longer life. The belt is made with a bi-directional joint giving you the option to run the belt in both directions. You can use the belt on either a power belt or bench top sander.