Shimano XTR Di2 RD-M9050 GS is an 11-speed electronic rear derailleur for mountain bikes, built for riders using Shimano Di2/XTR M9050 drivetrain components. The GS medium cage version is suited to 1×11 and 2×11 setups where a compact derailleur body and controlled chain wrap are more important than maximum cassette range. It uses hanger mounting and is designed around Shimano HG-X 11-speed chains. For buyers replacing a worn Di2 derailleur or building an older XTR electronic MTB drivetrain, this is the version to match when the bike needs a medium-cage rear mech rather than the longer SGS type. Manufacturer and dealer listings place the GS weight at about 289-290 g, with black finish and aluminum construction.