Campagnolo Centaur 11 speed rear derailleur. It must be used with Centaur 11 speed shifters and is not compatible with Campagnolo bar end shifters.
The rear derailleur differs from the higher tier mech in it's geometry. It is optimised for 11-29T, 11-32T and 12-32T cassettes or anything in between. You cannot use a 13T start cassette.
That's the compatability out of the way. What you get is a pretty rear derailleur that works very well.