Neckmike M4 Bluetooth Headset Twin Unique and patented headset enables communication in high-noise environments via Bluetooth or mobile phone and may be worn with or without a helmet Throat microphone based on military technology minimizes the influence of ambient noise such as wind, engines, traffic, etc. Noise-isolating stereo ear plug speakers block out unwanted outside sounds Full duplex intercom over Bluetooth at a range &gt;  mile (1,000 meters), toggling between up to 4 different riders / passengers (additional units sold separately) Wireless handlebar remote included (with built-in rechargeable battery)