They are precision ground, heat treated tools made from M2 HSS that easily cut through the stock rather than ripping, tearing, and pushing through as do typical hole saws. They can produce holes 3 times faster and cleaner than hole saws in sheet metal and have a dramatically extend tool life. The cutters are for producing holes from 11/16" up to 3" diameter in sheet metal, rubber, gasket or fiber materials, and some plastics up to 1/8" thick.