Some of the people in here have had problems with the shock reservoir hitting the frame cross member directly above it under compression, with newer shocks. I took a chance on a 2010 ZX6r rear shock and linkage and mine clears but not by much. With no weight on the suspension I can just fit a finger in between (reservoir/cross member) sitting on the ground you can't anymore, I don't have any marks on the shock or frame from contact but I think its pretty close as it is. You'll have to turn the regulator 180 degrees so it plugs in at the back to make some clearance for the regulator plug but mine went in pretty easily and improved the ride quite a bit, actually didn't feel like the same bike although I did the front with BPFs at the same time so I would have been disappointed if it hadn't. In my opinion the best thing you can do to these bikes is suspension upgrades, the stock rear just can't keep up when pushing it (not enough damping), making the rear feel loose and the front dives a lot under braking unloading the rear making late braking corner entries a bit of an experience because of minimal rear traction. I lost the rear on mine in just such a situation and ended up in a ditch, since upgrading my shock/forks/brakes I've gone around that corner at higher speeds than the day I ran out of road on it and stayed between the ditches. I don't think anyone has tried anything as new as 2015 as far as I know but they may or may not fit. How much of a gambler are you? My 2010 shock wasn't supposed to fit and did, if you take a chance and it doesn't you could always resell it.