I read another review warning that the volume may be low with some phones, even at maximum volume and that is indeed true for me with my a nokia E61 and a motorola phone I borrowed. The motorola was actually just slighly louder and almost usable at freeway speeds, but just barely. With the nokia, at full volume I just can't hear well enough to make out 100% of the conversation, and I have good hearing (again at freeway speeds).