Diablo's Steel Demon™ flap discs feature a premium zirconium blend for up to 10X faster material removal when compared to standard grinding wheels. The flap discs' special flap design offers flexibility and provides for a cushioned grinding effect. Diablo's high performance flap discs combine two steps in one by simultaneously grinding and polishing. Premium Zirconium Blend - a superior quality formulation designed for fast material removal and long sanding life Delivers up to 10X faster material removal than a grinding wheel Type 29 - Conical design Arbor - 5/8"-11 HUB