The C6 has three modes: FM, Bluetooth, and intercom. The intercom mode works like a walkie-talkie but without the need to push-to-talk. We keep talking like we are using cell phones. I have two C6's and one C9. The two C6's would connect as soon as they were turned on, without me having to do anything. The connection will break when the two units get too far, at a kilometer or so, or if blocked by a hill. When they are in range again, they connect automatically. My wife and I have used the C6 for skiing in Whistler, Canada for a week now, and we love it. The battery lasts more than 10 hours on a full charge. The voice quality is like that of a cell phone, with low noise or distortion, and there is no wind noise at high speed. The C6 does not connect with C9. I don't know what would happen if there are three or more C6's in range.I have also used the Bluetooth function to talk on the phone. The talk quality is good, and the noise is low. I tested the FM function. I tested the FM function. It works well.Each unit comes with a metal clip for attaching to the helmet, the main unit, and a headphone/mic unit. The helmet must have an outer shell layer and an inner shock-absorbing layer for the metal clip to be inserted between the two layers and clipped on the shell layer. I have a helmet with a unibody, and the clip won't work. It may be taped using double-sided tape. The headphones are attached to the inside of the ear cups using included tape.I highly recommend this for skiing couples and friends.