I bought my Plantronics 510 after having tried a similarly priced Motorola bluetooth headset. I returned the Moto, which had the inferior design of sitting outside the ear; this type will never have sufficient volume, don't bother with it. The best thing about the Plantronics 510: it comes with three interchangeable earbuds so you can custom fit it to your particular ear size for maximum comfort. The sound is so good with the 510 that callers often don't know you're even on a handsfree. The only gripe I can find is the on/off control is too close to the volume control and it's easy to confuse the two when wearing the unit. Beyond that, this is the one!