This belt uses tough aluminum oxide grain coated on a heavy "Y" weight polyester backing with a resin bond system. It is an open coat belt and its polyester backing permits users to wash their belts for additional savings. Aluminum Oxide Abrasive Grain - Aluminum oxide is extremely tough and has a wedge shape for high penetration of tough materials without excessive shedding or fracturing of the grain. Aluminum oxide is suited particularly well for grinding high tensile strength materials i.e. carbon steels, alloy steels, tough bronze and hard woods. Aluminum oxide is used whenever toughness ( the ability to resist fracturing ) is the main consideration. Aluminum oxide products are typically brown in color. Open Coat Abrasive Grain Coverage - Abrasive grains cover approximately 50% - 60% of the coated surface. Coat products generally offer greater flexibility, faster cutting, coarser finish and provide a greater resistance to loading. Open Coat products are used widely for woodworking applications, with limited applications for metal. Resin Bond Backings - Resin bond backings offer greater resistance to heat , are more durable in heavy stock removal applications and provide the best all-around bond system.