The bolt cover is used as a crank extractor for the Radius Cranks. When it is tightened in place with the aluminum hex wrench piece, the crank bolt with its 8mm hex can be reached through the larger hole in the bolt cover. The bolt is backed out and it acts as a jackscrew, lifting the crank off the spindle. The bolt cover has a Delrin washer in the back to facilitate the bolt removal. These are possible to come loose with very vibration prone riding, so we suggest using Teflon tape, the weakest Locktite 222, or even Elmer's glue to ensure that vibration won't loosen the bolt cover.