Polarstar A&K / JG SR25 spacer kit for Fusion Engine

The installation ring kit for A&K SR-25 comes with a Delrin spacer which placed at the front of the cylinder of the Fusion Engine so that the version 2 system has the same length as the original elongated gearbox SR25. An M5x0.8mm nut is also included to place on the back of the SR25 so that the original bolt can be screwed to the back of the system. This kit coupled to the A&K SR25 nozzle (purchased separately) allows the system to work with the original M4 type hop-up chamber of the replica.