After trying over and over again to tighten this rear luggage rack on my bicycle seat post so it wouldn't move, I finally had enough. And yes I did include the rubber pieces around the post and the rack with my installation attempts (one was not enough and two was too big for the rack to slide down). So I took it to Doudney Sheet Metal on 7-26-12 in Sarasota Florida and had it welded. Problem solved. They even painted the weld. A great job for sure. With my model bicycle this is the only type rear rack I could use.