Reinforced to cut stronger, last longer and resists tooth strippage. High speed steel teeth resist breaking and offer extended life. Thick backing plate with holes for drive pins resists damage due to high torque. 3-1/8 inch bi-metal hole saw. Reinforced to cut stronger, last longer and resist tooth strippageThick backing plate with holes for drive pins resists damage due to high torqueHigh speed steel teeth resist breaking and offer extended lifeBi-metal4-1/8 in. diameterUse this hole saw with a 2L, 3L, 6L, 7L standard arbor or a 2L, 6L snap-back arbor.