Black Oxide Drill Bit - 6 Pcs The HSS Tool Material provides good wear resistance in mild steels, soft metals (aluminum, copper,brass, bronze) and non-ferrous materials. The Black Oxide Coating helps retain lubricants to aid in wear resistance and chip flow. Features include... 5/16" Mill Diameter 0.3125" Diameter 3 3/16" Flute Length 4.5" Overall Length Black Oxide Coated 118° Point Angle 6 Pcs