You will only need one chatterbox for you and your passenger. However you will have to buy another helmet headset and cord for their helmet. The chatterbox has two headset hookups. Your passenger will hear everything that you do and you have the ability to put the Chatterbox into an intercom mode where the conversation will only occur between you and your passenger instead of being transmitted across the radio. One last note, make sure you get the GMRS version.qkfire said: