The MILWAUKEE Step Drill Bits with JAM-FREE Performance feature a dual-flute design delivering up to 2X faster hole times, up to 4X longer life and up to 50% more holes per battery charge than competitors. Ideal for drilling small and large-diameter holes in steel and plastic, these bits are Optimized for Cordless Drills in High Speed. The Rapid Strike tip allows for a fast and accurate start that generates less heat, resulting in longer bit tip life. Black oxide coating alsoenhances durability, hole quality and bit life. For user convenience and accuracy, 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 6-Piece Set includes bits #1, #4, #6, #7, #8, and #9. Jam-Free Performance in high speed with most professional 18 volt cordless drills with lithium-ion battery technology. The MILWAUKEE SHOCKWAVE Impact Duty Electrical Step Bits are engineered to deliver the most durable and fastest impact step bit hole drilling solution. The ¼" hex shank has an optimized SHOCKZONE body providing you with the industry's most durable shank. A Titanium Aluminum Nitride (TiAlN) coating helps deliver you 5x longer life, while the step drill bit's Rapid Strike tip and dual spiral flute produce 2x faster holes. The step drill bit kit features the #1 1/8 - 1/2", #4 3/16 - 7/8", and #9 7/8" &1-1/8" step bits with laser engraving for a clear stop on size identification.