SRAM Apex Eagle Rear Derailleur - 12-Speed, Long Cage, 52t Max, Black, D1The SRAM Apex Eagle rear derailleur quietly and quickly shifts across their 12 speed Eagle cassettes, while 1x specific chain retention technology keeps the chain where it needs to be. It's the best of SRAM's road and mountain bike innovations in one package. Compatible with 50t and 52t Eagle cassettes Works with SRAM 12 speed mechanical Apex and Eagle shifters For use with Eagle 12 Speed chain Roller Bearing Clutch controls chain tension for