Rear Seat Expansion Kit with Helmet Kits or Headsets expands a two-person intercom system to 4 persons, compatible with STX Stereo and Mono Intercoms. This kit includes headset and helmet options with 16' cables to reach back seats. The AlphaBass Headset impresses with genuine carbon fiber, leather ear seals, a Flex Boom Mic, an M101 Red dynamic noise-cancelling mic, and features adjustable volume and bass control. Alongside that, the Ultimate Mono and STX Headset offers a classy Carbon Fiber style finish, robust Flex boom mic, M101 red dynamic noise-cancelling mic, integrated wiring, large comfortable gel ear seals, cloth ear covers, and accessible volume control. Helmet Kits have Alpha Audio speakers and Dynamic Noise-Canceling mic. The package includes two headsets or helmet kits and two 16' intercom cables.