* While some manufacturers use recycled grains, Bosch uses only superior virgin grains made to exact specifications* Carefully formulated resinoid bonds are applied to meet the unique specifications of each wheel* Multiple layers of long, stranded fiberglass are woven to form an exceptionally strong reinforcement layer specific to the application* A30T-BF - Aluminum oxide grain, 30 grit grain size, toward the hard range on the bond hardness scale. Resin bond and fiberglass reinforcing* AZ30S-BF - Aluminum zirconium grain, 30 grit grain size, in the medium to hard range on the bond hardness scale. Resin bond and fiberglass reinforcing* AS30INOX-BF - Aluminum oxide grain specially formulated for use with stainless steel, 30 grit grain size. Resin bond and fiberglass reinforcing* AS46ALU-BF - Aluminum oxide grain specially formulated for use with aluminum, 46 grit grain size. Resin bond and fiberglass reinforcing* CS30S-BF - Silicon carbide special grain, 30 grit grain size, in the medium to hard range on the bond hardness scale. Resin bond and fiberglass reinforcing