The L.H. Dottie RTTP6040 Step Drill Bit Kit features a 1/4-inch to 1/2-inch extra tip, a 1/4-inch to 7/8-inch base and tip and a 1/4-inch to 1-1/8-inch base and tip. Each step drill bit has a 1/4-inch shank diameter. A real money saver because base bits last 3 to 4 times longer at a fraction of the cost. Economical replaceable tips lock in place. Step bit performance remains identical to that of non replaceable tip bits. Constructed of M2 high speed steel, coated with titanium and cobalt. Tri-cut tip cuts smoother, faster and cooler.