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 13-hole sizes from 1/8-Inch to 1/2-Inch (3.2 to 12.7 mm).