Piaggio Vespa Throttle Slide Cover (SI 24-26 E/G/H) PX 200, Cosa 200
The throttle slide cover holds the slide in place while the hook moves in and out of the action. 20mm have a slightly smaller cover in comparison to 24mm and 26mm cover.
As you can see, the throttle slide cover is held can a variety of different SI Carburettor types.
Comparison No. 0849100 53 (DELLORTO)