Made of M2 high speed steel. Cutters fit 3/8" and 1/2" hand held drill chucks. Includes 3 in a pack. Made in the USA This series cut holes 3 times faster and last 10 times longer than twist drills or hole saws, for precision hole making in sheet metal and frame materials up to 1/2" thick. Blair Rotabroach annular Cutters make clean, burr-free, round holes with no deforming of stock or damage to the surrounding material. There's no dead zone, so less thrust is required and no deforming of stock or jagged edges occurs. Multiple cutting teeth, precision ground which allows for a long tool life.