Hanger Genie is a bendable, precise tool used to realign rear derailleur hangers and maintain precise shifting. It is compatible with all wheel sizes from 20 ̋ to 29 ̋+ and screws directly into the rear derailleur hanger threads. The precise measuring gauge can be locked in place, so you don't lose your measurement when you push it against the wheel in different positions. Thanks to the rotating bottom part of the tool, you can easily disengage the frame as you work your way around the wheel.