Most of the chuck keys provided by manufacturer’s with their tools are virtually worthless. The standard “L shape” design doesn’t allow you to really tighten the chuck, which often results in bit slippage and a burr on the shank. These Ratchkey chucks are better than just simple replacements. The one-way ratcheting action allows you to tighten chucks faster and more easily, and the handles are large enough to allow you to exert the appropriate force (the steel-handled TwinKey can apply upto 135 inch pounds of torque, and the smaller, red handle RatchKey can apply up to 120 inch pounds of torque). Surprisingly, there is no standard size for chuck keys, and most of the installed chucks do not have any model number on them. That means selecting the right model is a bit tricky. To help you select, our web site lists many of the chucks each key will fit. Available in two styles: the TwinKey™ has two pair of different chuck keys at opposite ends of the steel grip, while the Red RatchKey has one pair of ratcheting keys on the end of an steel reinforced plastic handle. Note that Bosch tools typically use Rohm chucks. Made in USA.

The Ratchkey model HC-13 (A) will fit most 3/8" 10mm and 1/2" 13mm Jacobs style drills,
and also replaces keys (See Below)

REPLACES KEYS
3/8" (10mm) B&D (U1533) Jacobs (KK) Rohm (S-19) Supreme (B-13)	1/2" (13mm) B&D (U1508) Jacobs (K32) Rohm (S-9)