Straight, Double Fluted Step Drill Bits from Klein Tools provide cleaner cutting and drilling. The aluminum titanium coating is 10 times more durable than steamed black oxide for longer bit life. 3/8-Inch hex shank is durable, and has a firm, positive grip. Laser-etched markings provide quick size identification on primary holes. This step bit has 9-hole sizes from 1/4-Inch to 3/4-Inch (6.4 to 19.1 mm).