Nick. Seems to be very stable on the rack. No wobble at all.(motorway + speeds) Even with my weekly shopping from Sainsburys in it. It needs quite a bit of pressure to lock it onto the base-plate. which has rubber buffers that get compressed when the box is locked in place. My bike is a cruiser so the box wont be tested at Autobahn speeds. For the money I was very surprised at the quality. This also is "mono-key" if that means that one key is used to either open the box or remove it from the bike. John