The Universal Derailleur Hanger consolidates thousands of hanger options across the industry. Plus, if you ever need replacement, it will be available everywhere. The UDH. One hard-working hanger. Features: The Universal Derailleur Hanger - or UDH - consolidates thousands of mountain bike derailleur standards. The UDH is designed to rotate rearward in the event of impact and features the ability to \\\"re-rail\\\" the chain back onto the small cog. The UDH works with all commercially available MTB and E-MTB drivetrains from Shimano to Box to Sunrace.