This is Shimano's XTR M9120-SGS Rear Derailleur. This derailleur gives you the ability to use a 45 tooth cog in the back and a 2x up front, so when the trail gets steep you will be ready. The extra cog of 12 speed gives you more range and allows for smaller jumps between cogs to help you find the right gear.
- Decreased tension at low gear position to prevent high chain tension
- Bigger 13T pulley
Max Cog: 45T
Min Cog: 10T