Bulk pack. Made of carbon steel and fully austempered. Packed 10 per bulk pack. No. AEB-516-B: 1/2'' round center hole, 10'' x 2'' tapered cut, sharpened on 4 sides, fits MTD, John Deere, Little Wonder, and Power Trim No. AEB-521: 1/2'' round center hole, 8-3/8'' x 1-1/2'' straight cut, not sharpened, fits Black & Decker model No. 8220; OEM model No. 82-304 No. AEB-530-B: 1/2'' round center hole, 9'' x 2'' straight cut, sharpened on 2 sides, fits Sears, Western Tool, K & S, Cosco, Ruhman, Trim-All, and Moto Mower