This Kit contain all 4 cutters (1/4, 5/16, 3/8 and 1/2 inch) these Cutters are made of high speed steel (M2), used in either an pneumatic or electric drill. This bit capable of operating at speeds up to 2,000 RPM. It leaves a clean hole that requires very little grinding and has a self centering point that minimizes walking It will not require a punch and is a solid one piece construction and will not break or snap.