Vertix Velo Cycling Intercom (2 units) with Wireless Remote Control and Road Bike Headphones Group chat capability - stay connected to each other with an individual range of up to 500m between 2 riders and a total distance of up to 1.5km for 4 riders within line of sight - https://www.youtube.com/watch?v=bccSPsbHDIU Filter out unwanted noise with Cut-the-Noise technology and the voice activated microphone allows one to engage in real-time communication without the need to shout or press any button once the control units are paired. The Velo is IP54 certified, offering protection against both dust and water. It is suitable for all weather use. Once it is fully charged, it can last up to 10 hours. Enhance your safety with the wireless design, automatic answer of incoming calls as well as retention of environmental awareness. Low radiation - one tenth of mobile phone radiation level. The Velo complies with stringent Specific Absorption Rating (SAR) standards.