I've had a few different Motorola units including the HS 820 and both the European and US version of the HS 850. All models seemed to work well with my V-600 but I never felt the earpiece volume was loud enough. I recently bought a Plantronics 640 and I've never been happier. In fact, when my wife calls I usually have to turn down the volume On the other end, people have told me the sound was very clear. The only downside I've seen so far is that it's not as user friendly when it comes to turning on/off or when making calls using voice recognition. It's a small price to pay to actually hear the conversation without pressing the earpiece up tight against your head though.

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