Velcro - The diameter of the Velcro is 2 inches and is suitable for most types of rotating tools, such as: B. Die grinding machines, air grinding machines, drills, etc. Soft foam buffer cushion - The grinding wheel kit contains a 1-part soft foam buffer cushion. Make sure that the soft foam buffer cushion is firmly connected to the grinding discs and the backing plate before use. Quantity and practical set - pack contains 200 pieces of grinding wheels, 10 grains, 20 pieces for each grain: 80/180/240/320/400/600/800/1000/2000/3000 1 pc 1/4 inch shaft support plate and 1 pc soft foam buffer plate, large quantity to meet your various polishing needs. superior material - made of alumina abrasive, durable and anti-static, useful for cleaning and polishing corners, such as polished metal, wood, jade and so on. Warm note: These grinding wheel pads fit a 2 inch backing pad, which is not suitable for self-adhesive grinding pads. Please clean the dust and replace the old sanding block before using it.