The M772 XT SGS derailleur is Shimano's Shadow design in long cage option. Perfect for riders using the more common 34t cassettes. It also allows cross shifting under load.
The Shadow derailleur is tucked in under and behind the cassette, it is less likely to be damaged from the perils of off road riding. The shifting performance is also improved due to the closer position to the cassette. The Shadow design places priority on a low profile design and less body movement for increased performance and durability.
In high gear, the derailleur has a profile that is a full 15mm less than a traditional rear derailleur. That means it barely protrudes more than the quick release skewer nut. Shadow design also minimizes annoying chain slap.