The "shim" works perfectly. But it does not attach to the mount and so when you take the light off the bike the shim falls off. My first one is lost in a gravel drive as a result. Have ordered two more. Noteworthy that the equivalent shim for a shapesd seatpost has a rubber protuberance to make it stay in the mount

Please design and make a bracket for aerobars. These inserts are not fit for purpose and can vibrate loose on rough ground. They are also easily lost. My front light came off a few days ago and smashed on the tarmac.

These inserts are not really fit for purpose. On rough surfaces the vibration causes them to move around. Today my front light came off and smashed on the tarmac. What is needed is brackets specifically designed for aerobars, D shaped seat posts etc.