Finding a cellular headset that was usable in loud background environments (mainly the car) was not easy. This was the fifth (and last) try before I gave up. The 645 is almost too lightweight and I fear loosing it. The pocket holster does not positively hold the headset, so unless it is held upright, use caution. The three sizes of earpieces provided are very comfortable. The optional over ear wire is not really needed unless wind is an issue (convertibles, bicycles, etc.)
Posted by: Allen Hirashiki - Fabric7 Systems Inc. - Mountain View, CA