Weiler 51165 Tiger Paw XHD Super High Density Abrasive Flap Disc, Type 27 Flat Style, Phenolic Backing, Zirconia Alumina, 4-1/2" Diameter, 5/8"-11 Arbor, 40 Grit, 12000 RPM (Pack of 10) 100 percent zirconium grain greatly increases cut rate and product life Superior grain retention provides maximum aggression on edge Engineered poly/cotton cloth eliminates premature shedding and maximizes disc life Contaminant free cloth contains &lt;/= 0.1 percent of iron, sulfur and chlorine Phenolic prevents backing from scratching the workpiece