The L.H. Dottie RTTP6010 Step Drill Bit is a 1/4 inch to 7/8 inch step drill base and bit tip that fits 9/16 inch, 11/16 inch, 3/4 inch, 13/16 inch and 7/8 inch step sizes. 1/4 inch shank diameter. A real money saver 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.