yup, Stew is on the money
PE250B/C RM250/370/400 and DR should all have the same coarse spline.
The later N and T models are the same size but mounted via a bolt into the shaft not a pinch bolt so these are a no go.
The RM400C kicker which is more or less typical fits ok but it does hit the exhaust when it's folded in. Even so it tucks in way better than std. The only real issue I think you'll have is the damn thing will rattle against the pipe
Will have another look tomorrow and try and post some pics showing the interference