This will adapt any 1/4" hex bit to work with a 15mm wrench for use in tight areas. In my case, I needed to remove rear deck speakers from a 2005 Ford Mustang. The rear-most screws are only about 2" from the rear window and a ratchet or screw-driver just was not getting in there. This adapter let me use a 15mm gear-wrench and got the job done nice and quick. Sorry for mixing SAE and Metric, I intended the wrench size to be 1/2", but my measurement incorrect. However 15mm works fine.