This is the Casa Performance timing disc that we have had manufactured as we wanted to resolve the problems we have encountered when using discs from other manufacturers. Firstly, we have had them made in 2mm thick aluminium so they'll last for years without breaking up, as is always the case with plastic timing discs. Secondly, we have added the degree numbers in BOTH directions for the full 360° of the entire circumference, so they are also perfect for both setting the ignition timing and for checking cylinder port timings. The discs were primarily manufactured for use when fitting the Ducati Firefly 12V electronic ignition systems that Casa Performance produce, but they are perfect for any ignition you wish to set up on a smallframe model. If you have a Lambretta J range or Luna Line scooter in your garage or workshop, then you should have one of these, period!Outside diameter of the disc = 144mm.