This works very well with my Nokia N75 but the speaker power is too weak when I'm driving my noisy Mustang GT. It's little bit strange because from 12V battery you should able to get 3-4W to 8 Ohm speaker. I'm going to open the case and change speaker driver if possible.I think that this is not Nokia design because usually they do not design or manufacture any accessories. Usually Nokia specifies everything very carefully to OEM manufacturers so I'm surprised to see that output power of speaker is too low for real application.UPDATE: HF-33W died just two weeks after warranty expired. Great!!!