I believe it is a 120mm stroke damper you will need and the bracket will probably be either 50mm or 52mm, possibly 54mm as I am getting old and can not remember that well. I did this conversion too but with a WP damper and bought a 50mm bracket and had to return it for a larger one, the RS pipes have different dimensions on them so take care about that where you are planning to attach your damper. Hope that helps a bit. Cheers