Constructed using precisely engineered iron, sulfur, and chlorine-free resin technology, QUANTUM3™ (NQ3) Depressed Center Grinding Wheels provide uniform abrasive distribution throughout wheel. Unique bond was designed for retaining grains long enough during and after grain fractures, optimizing cut rates and wheel life. Offered in 4 x ¼ x 3/8 in. to 9 x ¼ x 7/8 in. sizes, wheels come in 12 Type 27 all-purpose models, 1 Type 28 all-purpose model, and 2 Type 27 models for foundry applications.