With all the drills in my shop, I never seemed to have the right chuck wrench when I needed it. Worse, the common L shaped wrench that came with most of my drills was just about worthless. These two wrenches each have four different size chuck keys on them. Between them they fit over 1200 different chucks: the smaller one fits most 1/4" and 3/8" chucks (Tips measure 0.220", 0.230", 0.240" and 0.270"); the larger one fits most 1/2" drill press chucks. (Tips measure 1/4, 5/16 and 3/8)