The factory sent over a batch of our new inner barrels, however instead of the 6.02mm inner bore these measured at 6.00mm.  Consider these real tightbore, they still work the same, tested with a range of BB's at the max size 5.95mm (BBLS, ASG etc).  The hop window measures 6mm long and 4.5mm wide.  The extra length and width allows for a slightly larger hop rubber patch, best results are with buckings like the Maple Leaf MR.

We've been testing these for several weeks now and have been getting excellent results. Internal polishing is high, RA 0.3-0.5 which is on par with Prometheus barrels, as a comparison ZCI is RA 0.8-1.0, please check out the comparison video below.

* We clean and test each one before we send out, ensuring level flight. 
* We offer a 90 day no-quibble returns policy should you experience any issues.
* Designed with larger patch hop rubbers in mind, such as the Maple Leaf MR.

We have 6.03mm and 6.05mm versions of this inner barrel arriving March/April.