We love tools that serve multiple purposes and act as many tools in one. The Bionic Wrench is just that. It solves a number of problems when using adjustable spanners and box-wrenches. It uses six hardened-steel blocks in a circular enclosure that actually become the jaws of the wrench and close down onto the six edges of the bolt no matter the size.
It will tighten on the bolt as you push whether tightening or loosening, making it easy to fit any sized bolt head and handling all sizes in one tool. The Bionic Wrench is available in several different sizes from $19.95.