First off, I'm using just the arm part of this mobile hanger, and I'm glad I dont need the mobile rotator (because it lasts less than 3 minutes and is extremely noisy and takes a lot of effort and noise to crank). I'm using a Shiloh battery powered mobile music rotator instead that is perfect. I bought this for the extra height over other mobile arms. It assembles easy enough. For installation, it will work best on a crib with a flush inner rail. My top rail has a half inch overhang that causes this arm to sit at an angle. I will probably create a shim to push the bottom out flush with the top rail contact point. I would buy this again.