The SPM-1400 "PATRIOT™" is our Medium Duty Headset with single speaker and Noise Canceling Boom Mic. The SPM-1400TR is the replacement Headset for the Tactical Kit version of the SPM-1400 and has a 5-pin DIN connector that plugs into the Tactical Kit's PTT switch. Use the MR-1400TR to repair your SPM-1400T Tactical Kit or to convert other Tactical Kits to a Boom Mic model.