Plastic Shim for Distributor Trigger Ring

Don't know how you can even post it for the price

After fitting a Powerspark ignition kit to my Lucas 25D distributor I found 8º difference between No1 cylinder and No4. Probably due to the magnetic trigger ring being loose. On questioning the supplier I was told hat a sim is available to tighten the 'ring onto the cam lobes. Cost is £1.00. After fitting the shim, a thin clear plastic device, the timing was virtually the same on Nos 1 & 4. Perhaps the shim needs to be supplied with each 25D kit. I had tried another distributor with the same difference between cylinders.