Carburettor - Dellorto slide needle clip
The circlip fits on the needle to stop it falling through the slide.
You can also order the small spacer shim to give you a half height adjustment on the needle clip here: http://www.lambrettaupgrades.co.uk/apps/ webstore/products/show/5435957
Suitable for any Lambretta or Vespa fitted with a Dell orto type carb
Price includes VAT @ 20%