SRAM X01 Eagle AXS Rear Derailleur - 12-Speed Long Cage 52t Max Battery Sold Separate BLK/RedThe Eagle AXS derailleur is the brain of the whole AXS system Shorter cage for 10mm more ground clearance, with more chain wrap on the cassette to sit slightly further forward, and further inboard from mechanical Eagle Battery not included SRAM Model ID: RD X0 1E A1 Specifications: RD Capacity 42T Speed 12 Minimum Cog 10T Maximum Cog 52T Primary Color Red