Ferrule for the gear cable in the headset for the Vespa PX etc. Made by SIP.
 
The gear and throttle outer cable ferrules sit in these stops in the headset bottom. This bush both centres the cable in the recess of the headset and also aligns it with the gear and the throttle pulleys. This not only makes changing gear and opening the throttle easier, it also means your cables will last longer. 
 
 
2 are usually required, price is for 1.