The Full Mount derailleur will only fit on a bike frame that follows SRAM's UDH derailleur hanger standard. There's a good range that do, but equally plenty that do not, although more gravel bikes ...

So in 2019, the US component giant delivered the SRAM UDH – Universal Derailleur Hanger – and created one of the most highly compatible mountain bike components ever made. To quote the Shamen ...

SRAM's UDH (Universal Derailleur Hanger) has been widely adopted over the last few years as brands look to give customers and retailers a simpler solution when it comes to sourcing spare hangers.

Bike-specific direct-mount hangers are available for Shimano rear derailleurs, but this is the first SRAM UDH to Shimano direct-mount adaptor we’re aware of. Shimano’s direct-mount standard ...