Honda HRU19R what is this part of the carburetor called

[hebiebug]

Hi all,
Really stuck could someone tell me what this part is called?
When I took the carbie off the mower I ended up with this in my hands.
Would like to know what it does and if I can't get it back on can I lock tight what's left?
Thanks in advance

 

[hebiebug]

Discovered.
It a pilot screw (16016-ZG0-W00) and if anyone is interested here is a write up on it
https://www.howtomotorcyclerepair.com/how-to-size-your-pilot-jet-pilot-screw-explained/
Happy days