I’m not sure but the R might indicate that there is a sleeve around 4″ long inside the axle with holes in it that line up with the keyways in the axle. The sleeve is normaly driven in and positioned where the sprocket clamps on. I think it’s more to prevent crushing the axle with the sprocket and to provide a little more thickness for the key. The hard swift axle comes with that piece in it or if you have one it could be removed from the old axle. Push it out the side that’s not bent.