This part sits in the accelerator fuel passage between the two halves of the GL1100 carburettor plenum.

It is there purely to reduce the volume in that passage. It does not actually connect to anything at either end.

The original Honda part was a rigid plastic tube, no longer available. This is a softer silicon tube to exactly the same dimensions as the OEM tube. This material will not be affected or hardened by anything in the fuel.

There are alternatives out there but at much greater cost than this part.