Innovative zirconia grit gives Dewalt type 29 flap discs the power to remove material 3 times fast than fiber resin metal sanding discs. Type 29 fiberglass backing provides a grinding angle of 20-25 degree. A premium abrasive cloth offers a life up to 15 times long than fiber resin metal sanding discs. Zirconia grit enables 3 times faster material removal than fiber resin sanding discsPremium abrasive cloth provides up to 15 times longer life than fiber resin discsType 29 fiberglass backing provides angle of 20-25 degrees4-1/2 in. diameter with 7/8 in. arbor hole60 grit