This is one of those things every Lambretta owner should have an extra on the shelf of.
I don't know how many times I have torn one of these when I had intended to reuse the old one only to find I didn't have another one on hand to use.
That totally sucks when it happens. Don't let that happen to you, buy an extra!
Athena brand chaincase cover (primary cover) gasket fits all S1-GP/DL Lambrettas except the TV1 (big surprise I know)