4-1/2 in with 7/8 in arbor. For right angle grinders. Cuts fast and outlasts sanding discs. Multiple layers of zirconia cloth flaps constantly exposing new extra sharp grinding points. Laminated by state-of-the-art automated equipment. Reinforced fiberglass backing plate. Each disc balance tested for vibration-free grinding/finishing. Wheel size: 4-1/2 in, arbor 7/8 in, maximum rpm: 13,300, tool type: right angle grinder.