Shimano XTR M980 10S Shadow Rear Derailleur
The Shimano XTR M980 Shadow rear derailleur is a 10 speed long cage rear derailleur. It has the original Shadow technology which tucks the rear derailleur in a little closer to the frame reducing the chance of your derailleur getting bashed on a rock, root or stump.
I've had this derailleur for a few months now and nothing but crisp and precise shifting in any conditions. I'd recommend the version with the clutch... it keeps the drivetrain nice and tight. No slap!