This closed coat aluminum oxide belt uses a "X" weight 65/35 polyester/cotton backing with a resin bond system. It is suitable for sanding and fine finishing wood as well as ferrous metals where extra fine finish and/or flexibility are required. 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. Closed Coat Abrasive Grain Coverage - Abrasive grains cover 100% of the coated surface. The greater number of abrasive grains normally results in a better finish and a higher amount of stock removal during the useful life of the product. If loading is not a problem, a Closed Coat product will give you superior life and lower cost. Closed Coat products are widely used in metalworking and woodworking applications. 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.