Hard tempered spring steel blades are designed for use with the ALL10260 ALL10270 and ALL10590 Heated Tire Groovers Blades are honed to a razor like finish and have a tapered shape making the blade wider near the top where strength is needed and thinner at the bottom greatly reducing drag as the blade cuts through the rubber Blades are sold in packages of 12 Note Do not use these blades in "ALL-IN-ONE" style groovers!