Milwaukee® Step Drill Bits with JAM-FREE Performance feature a dual-flute design delivering more holes per battery charge than competitors. Ideal for drilling both small and large-diameter holes in steel and plastic. These bits are Optimized for high speed cordless drills . The Rapid Strike™ tip allows for a fast and accurate start that generates less heat, resulting in longer bit tip life while the black oxide coating enhances durability, hole quality, and bit life. For convenience, each bit has laser-engraved reference marks you can see while drilling. The 3-flat Secure-Grip™ shank ensures a solid connection with the drill chuck. The Step Drill Bit 4-Piece Set includes bits #1 (48-89-9201), #4 (48-89-9204), #7 (48-89-9207) and #12 (48-89-9212). Jam-Free Performance in high speed with most professional 18 volt cordless drills with lithium-ion battery technology.