I installed a full cage so I no longer need the Brey Krause R-1202 harness bar from my M3. This was in a dedicated track car for one year / approx 500 miles and is pretty much new. Fits all E46 coupes and mounts to the factory seat belt attachment points. BK tests their safety gear to SAE standards so you can be confident that this will do its job in case of an accident.
I went with a harness bar and not a 1/2 cage to optimize the height of the harness mounts prior to going full cage. I found that all commercial 1/2 cages (Rogue, VAC, autopower, etc) mounted the harness bar too low to safely use HANS with my height and seating configuration.