SRAM GX Eagle Rear Derailleur - 12-Speed Long Cage 52t Max LunarThe GX Eagle Rear Derailleur gets the job done with a thoughtfully designed cage architecture that improves chain management. Mounting system and re positioned Cage Lock offer greater durability Sealed cartridge pulley bearings Rear Derailleur Mount Type 10x1 Standard Rear Der Shifter Compatibility SRAM X Actuation Cage Length Long Drivetrain Speeds 12 Color Lunar Chain Wrap Capacity (teeth) 42 Largest Cog 52