Made of premium High Speed Steel with excellent hardness of HRC 62-64, it provides superior cutting power, high durability, and good abrasion resistance. Perfect sized hole for #6, #8, #10, or #12 screws. No. 6 - 3/32" Pilot No. 8 - 7/64" Pilot No. 10 - 1/8" Pilot No. 12 - 1/8" Pilot Lumberjack Quick Change 1/4" Hex Shank Adjustable Countersink Drill Bit Set in Black