JACK is a centerline AEG cylinder replacement. If the gearbox uses a standard piston and cylinder assembly and the nozzle is centered in the cylinder there is a good chance JACK will fit.In order to install JACK into an AEG, the correct nozzle is required. PolarStar manufacturers a number of different JACK nozzle lengths to cover a wide range of guns. If the nozzle length you require is not already in production, custom nozzles can be made upon request.In addition to the nozzle, JACK must interface with the selector and trigger of the host gearbox. This is accomplished using various switchboards which install into the gearbox shell.For more information on the compatibility of specific models please see our Compatibility Guide in the support section.