IRWIN Unibit 3 8 in 13 Step Drill Bit Flooring new 15 Slip resistant comfort soft grip Attachment Options:w Combination Bit Set (65 Pieces) Slip resistant comfort soft grip Add smooth mobility to carts and shop projects with these 3 inch WEN swivel plate casters wood and laminates 3 flatted shank won't slip in chuck Speed point tip for fast starting Laser marked sizes won't wear off with use Unibit #3 is engineered with M35 cobalt steel for maximum life when drilling in tough steel Unibit #3 cobalt contains a 3 8 in hex shank and contains 9 hole sizes 1 4 in 3 4 in (1 16 in steps) Unibit #1 contains a 1 4 in hex shank and will drill 13 hole sizes 1 8 in 1 2 in (1 32 in steps) Unibit #4 contains a 3 8 in hex shank and will drill 12 hole sizes 3 16 7 8 in (1 16 in steps) Single fluted cutting edge for greater control and rounder holes Ideal for drilling holes in thin materials such as mild steel