These Double-Fluted Step Drill Bits provide faster cutting and drilling than single flute bits. The easy-to-read step markings and targets save time when drilling holes. Thick 3/8-Inch hex shank provides a firm, positive grip and won't spin out in the drill. KTSB15 7/8", 1-1/8", 1-3/8" STEP BIT 3-STEPS