Good evening What is the difference between the Pure Highway 400 and 600? According to the description, the 400 is missing the hands-free kit. Is it possible that only the microphone is missing from the scope of delivery of the 400 or is the device technically different from the 600? Does the hands-free system on the Pure Highway 400 work with the following microphone: Item 13090628 ??? Thank you very much for your answer.