What part is this

[Asony101]

What is this and where can i get them

 

[grepper]

It's a Jet Plug.
http://4into1.com/k-l-carburetor-rubber-passage-plug-honda-cb-cm400-cx500-cb750-cb900-cbx/

 

[amc49]

You MUST have them too if the carbs came with them, some don't but fuel circuit changes made to suite that.