DEWALT DW8212 4-1/2-Inch by 7/8-Inch Z80 T27 WB Flap Disc Backing automatically wears down with cloth to allow full use of cloth increasing life by 2x's Extended performance flap design lasts 2 times longer than std flap discs Premium zirconia cloth prodives agressive grinding action 50 percent faster than std flap discs Proprietary design provides removal rate of a grinding wheel with finish of a fiber resin disc Max Rpm of 13,300