This OEM rear sway bar is a very easy install that fit Mazda 3's. I took this off my speed 3 at 11,000 miles. Nothing wrong with it what so ever.
Includes the bushings and the installation instructions.
I have the bushings brackets. All you need are the bolts. I think your M3 already has the bolts but I am not sure. This is a very easy instal. It tool be 1/2 hour. I'll send you the instructions with the sway bar.