The NX Eagle rear derailleur features the proven SRAM 1x-specific X-HORIZON design. The larger, 14-tooth X-SYNC lower pulley easily facilitates 11- to 50- and 10- to 50-tooth cassette capacity, and also adds to NX Eagle's overall smooth-pedaling feel. The Type-3 ROLLER BEARING CLUTCH provides quiet, consistent performance and durability.Mounting system and re-positioned Cage Lock offer greater durabilityEagle pulley technology provides greater efficiency, crisper shifting and quieter operationDesigned to be used with Eagle 12-speed chainsLong cage with 50 tooth max capactity