This new part from Casa Performance has a double purpose.

With the advent of the forthcoming 'Casa 135' cylinder kits for smallframe Lambretta Lui / Vega / Cometa and J range models, there will be a necessity to mount non-original type exhausts onto engines that, in the main, do NOT have the extra lug that is an integral part of the 75cc 4-speed casings. These 75cc models have an exhaust that mounts to this lug. All other Lambretta Lui 50cc, J50, Cento, J125 3-speed and J125 4-speed Starstream models do NOT have this exhaust mounting lug.

This ring instantly resolves that problem. It fits directly under the flywheel cowling as it has same 5 holes that correspond to the actual cowling holes, but also has an additional part for mounting an exhaust! The two holes in this extra part correspond to the holes of the integral lug of a 75c casing, as can be seen in the pics.

Lambretta 50cc machines (both Lui 50 and J50) have much shallower flywheel cowlings than their larger 75, 100 and 125cc counterparts. The difference in the depth between the two types of cowlings can be rectified with the use of this spacer ring. For example: if you have a J50 with a standard type 4-pole ignition and wish to upgrade to a 6-pole or electronic ignition - which usually have a flywheel fan with longer fins - you would normally also need to fit a 75, 100 or 125 deeper-type flywheel cowling so the flywheel doesn't rub on the inside of the cowling. This ring resolves that problem as you can now maintain your shallow-type 50cc cowling. 

The material used is high quality 4mm thick stainless steel.