This PolarStar M249 Hollow Grip Bolt and Nut is what you would find included with your PolarStar HPA unit such as the Fusion Engine, Jack, F1, or F2. This Bolt comes with a channel through the center so that you can run your macro line through it and your pistol grip. Please keep in mind that this is designed for 6mm macro line. Larger lines such as our Integral Grip Lines (IGLs), will not pass through this bolt and will require modification to the rifle/grip in order to allow the IGL to pass through.
