Literally this.

My dad has two, both slightly different in design. They're not bad for leg bolts, but not much else. Like nman said, the head is really large, so if you're planning on using it in a backbox, you might run into room issues. Also, the head part is very "thin" so gripping things dead on can be a challenge unless you can rest the tool against whatever the bolt is screwed into.

Cool in theory, clumsy in practice. Stick with a decent socket kit, imho.