Shimano Rear Derailleur M8000 Deore XT GSShimano XT RD M8000 Rear Derailleurs 46 tooth maximum rear cog for 1x11, 42 tooth maximum for 2x11 and 40 tooth maximum for 3x11 Low profile derailleur cage reduces collection of debris and potential for damage Shadow clutch reduces chain slap and dropped chains, on off switch allows for simple wheel changes Externally adjustable clutch for easier spring tension adjustment Optimized slant angle lowers shift effort while improving shifting and driving