I seem to have a surplus of seats for 500/550 which are taking up space so need to move them on. There is a 500 four repro seat with the plastic base which i bought from a forum member, it looks new or near new and i did try it on my 550 for size and seems to fit well. I would like to get my money back so £100. I also have a repro 550 f1/f2 seat, it does look good but tried it on my bike and did not fit without some fettling so £40. Thirdly i have a cafe racer style with a rear hump that fits the same bikes, has a small split but looks ok, £25. will post pics soon