See that ramped fin that extends above the hanger? It's there to guide the chain back onto the cassette if it happens to get bounced off one of the smaller cogs.

Word is that the hanger is designed to rotate backwards if the derailleur is smashed into something. It doesn't return on its own - you'll have to dismount and push it back into place - but I suspect that it takes an uncommonly hard hit to make it move. The UDH works with all current derailleurs. And yes, current derailleurs also pivot backwards themselves, but in the future they might not need to if that functionality can be built into the hanger.



There's also what looks like a ramped fin that extends above the hanger. It's intended to help guide the chain back onto the cassette if it's bounced off one of the smaller cogs towards the frame. This should put an end to getting the chain jammed between the cassette and the frame, a rare but annoying occurrence.

The UDH is designed to rotate backwards if impacted hard, hopefully saving both it and the derailleur in a worst-case scenario.

The 2020 Trek Fuel EX that I reviewed last month had the UDH.

There are a bunch of places on a bike where I suspect that we'd all love to see some uniformity applied. Seatposts, hubs, and bottom bracket dimensions, and of course down at the derailleur hanger. We'll have to keep waiting on the first three, but SRAM is moving ahead with their $15 USD Universal Derailleur Hanger to tackle the latter. Not only is it just $15, but it's also open-source; there are no licensing fees.Why should SRAM do this if bike companies already use their own hangers? That's actually part of the problem, with some brands deciding to use dozens (or more) of different hanger designs over the past few years. Do you need the hanger from 2016 or 2017? There's a good chance that they're different, so you better know the answer. Maybe just before you're about to leave on a road trip? That'll be a two-month wait. An absolute nightmare.Conceptually, having a single hanger that's used across different brands and different bikes makes sense, even if there are countless variations out there already. A case of better late than never, you might say, just as long as enough brands get on board.In a way, it makes sense that companies responsible for drivetrains should also be responsible for the derailleur hanger. SRAM wants consistency because it means fewer variables and fewer opportunities for things to go south; if they can control the hanger's geometry, they'll know precisely where the derailleur sits in relation to the cassette. Fewer variables, more consistency, and likely better shift quality. Think of the possibilities with electronic shifting, too...No, they're not forcing frame manufacturers to jump on board with a proprietary system; it doesn't require a different derailleur - anything current will work just fine, including those from Shimano. There are already bikes in the wild using the UDH, including the 2020 Trek Fuel EX that I reviewed not that long ago, but expect to see more in the near future.Does it make sense? Should drivetrain companies also be responsible for derailleur hangers? Or are you doing just fine with the way things are?