The PolarStar wire harness is constructed with 24 AWG wire for superior continuity and features a nylon mesh sheath to protect the wires as they pass through the replica's body. These harnesses are universally compatible with all PolarStar electro-pneumatic HPA systems excluding the original V2 GEN1 Fusion Engine and Amoeba kits. - Compatible with any PolarStar system that uses a REV2 or REV3 FCU. - 18" is standard length for V2 kits in F2, F1 and JACK. Also recommended for FE's being installed into full stock replicas (e.g. M16A3). - 13" is standard length for V2 FE as well as V3 F2, F1 and JACK kits. - 7.5" is standard length for V3 and MG FE kits but is also recommended for wiring the FCU to the pistol grip with UGS/CGS installs. Black: Nozzle (not used for JACK/F1), White: Poppet, Red: Selector, Blue: Trigger, Brown: Ground