I believe that they are slightly different, but I think that a 250 hub would do the job for me . An RM500 guru told that the 500 hub is a bit more beefed up where the spokes go through . The OEM RM500 wheel has a 2.5” wide rim , where I think that the 250 is around 2.15” wide . The bike I am planning to use it on , is an ‘85 RM250 frame fitted with an RM500 motor , so I will probably look at getting a 2.5” gold anodised rim laced up to the rear wheel .