Fox RP23 Boostvalve Pro-Pedal Rear Shock 165/38mm, never used. 

Shock was taken off a new frame and replaced with a different make, so has just been stored since then. 
Hopefully the photos should show all info needed, but just to clarify - on the side of the shock, it lists:- 
Boost Valve Tune 225
Rebound Tune M
Velocity Tune L 

If you have any questions - please ask.