Weight: 180g for long cage (SGS) version.
Features a carbon fiber outer plate but an aluminium inner plater (the 9-speed XTR has both inner and outer carbon fiber plates).
11-speed compatibility?
Quite surprisingly, the 10 speed rear derailleur will work as an 11 speed rear derailleur if you use an 11 speed cassette and shifter. It will also work with an 11 speed shifter to shift just 10 speeds on a 10 speed setup. This is how I achieved a neat cockpit with my XTR M9000 brakes and M9000 11-speed iSpec II shifter pods; More info on mixing 10 speed casssettes, derailleurs and 11 speed shifters here.
Where to buy?
Amazon's got you covered with every option of XTR RD, sometimes with good prices too!