I bought this Siebenrock power kit two years ago in Germany. It was designed for 800 cc boxer engines but at BMW Bayer they also offered it for the /5 series. The bottom of the cylinder was lathed down so that it fits in the smaller opening of the crankshaft housing. Some people advised me against installing it because the /5 motor blocks have some weak points. However, I am not going to use it with full power in the Philippines where road conditions are so bad that going at fast speed would be life treating. I installed it with 2 years delay. Piston displacement was increased from 750cc to 1000cc.