Piaggio Vespa PX, T5, Cosa Throttle/Gear Tube Pulley Clip
The Throttle/Gear Cable Pulley clip is used to connect the pulley to the end off the throttle & Gear cable Tube. On both tubes you will find two holes that will hold this part in place securing the tube correctly.
Comparison No. 137267 (PIAGGIO), SF504-1131 - SF5041131 (LML)