Skinners Union units! It's hard to tell what size.
I had a Japanese mechanic working for me 20 years ago and he loved them.
He stuck them on anything and everything he could that needed air mixed with fuel.
I must admit that he always had sweetly tuned machinery using them.
BTW the 2" also hide an injector quite well if your in a class that doesn't allow FI.
There's a bloke that ran a Harley here in Melbourne years ago that did.
Even though it was difficult to hide the pump and wiring etc. he pulled it off.