This piece allows Caliburn users to use multi-part barrels with the railgasm kit for better dart fit. It replaces the first piece of the railgasm kit, and fits a standard CPVC Coupler. On one side is a small sections of standard Caliburn barrel, on the other is your barrel material of choice.

It still works with the stock barrel.

Parts required for picture barrel:
The PETG is here: https://www.mcmaster.com/mv1519231275/#catalog/9245K25
Couplers are here:https://www.mcmaster.com/mv1519231275/#catalog/5035K61

Also available on my etsy:
https://www.etsy.com/shop/Remzak