CGW depressed center grinding wheel. Excellent ratio of stock removal/wheel loss. For working on flat grinding surfaces. Most efficient when used between 0 - 15 degree angle. The best choice for smooth finishing. Arbor hole size: 5/8-inches - 11. Grit: 24 (coarse). Grade: R (hard). Specification: A24R. Maximum operating speed: 13300 rpm. Type 27 - depressed center flat wheel. Use for right angle grinder. Measures 4-1/2-inches diameter by 1/4-inches thickness.