2 x 180mm Shimano XT Centrelock rotors (RT79). These:
Both include new, unused lock ring.
Both rotors are boxed. One is brand new and unused, the other has been used for maybe 20 miles max (new lock ring).
New one: £25
Used one: £20
Email me via address in profile if you're interested. I'm pretty sure i have a 180mm rear mount/adaptor somewhere as well if that's of interest.