I previously owned 3 of this device's predecessor, the Jabra Pro 935 (one for my work office, one for my home office, one for my wife). Unfortunately, I bought them all around the same time, and within about a 2 month span, the battery on each gave out. And according to all research, they weren't replaceable. As they were a bit expensive, I went down the road of Bluetooth headsets. This was fine at first, but not sure why, but my last 3 work laptops have had Bluetooth issues (which was why I've had 3 different ones in the last 3 years - in troubleshooting I/T would give me a different laptop thinking it was hardware). I just could not get a Bluetooth headset to work with them consistently - nearly daily I would have to re-pair the device or restart it mid-day or take some other ... Read moreI previously owned 3 of this device's predecessor, the Jabra Pro 935 (one for my work office, one for my home office, one for my wife). Unfortunately, I bought them all around the same time, and within about a 2 month span, the battery on each gave out. And according to all research, they weren't replaceable. As they were a bit expensive, I went down the road of Bluetooth headsets. This was fine at first, but not sure why, but my last 3 work laptops have had Bluetooth issues (which was why I've had 3 different ones in the last 3 years - in troubleshooting I/T would give me a different laptop thinking it was hardware). I just could not get a Bluetooth headset to work with them consistently - nearly daily I would have to re-pair the device or restart it mid-day or take some other measure to get my computer to recognize my headset. So I decided to seek out the current equivalent of my much loved Jabra 935. Jabra advised me that it was the Engage 65, and if I wanted the ear hook which I had used on my 935, I'd need to get the "Convertible". I have a larger melon than most, and plastic over head bands tend to have a short life with me. However, I'm glad I did a little more reading! The Convertible model, while it did offer the ear hook, has a shorter day-to-day use battery life, AND the battery is not replaceable. On the other hand, for the Mono, it boasts 4 additional hours of talk time per day, and you can buy both replacement headbands and batteries (and they're not crazy expensive)! Still, the price for a new one was a little out of my budget so I went shopping for a used, figuring as long as it wasn't physically damaged, I could replace the battery if needed. And it has been awesome. It works great, no weird disconnects. The battery life isn't quite the 13 hours a new one would boast, but I could get a battery replacement for <$40. I'm also not using this device to its fullest capabilities. You can actually hook it up to a desk phone as well as a PC, and use it for both. Or if you're in a call center with other people using the same headset, you can actually conference people through the headset, not the phone itself. Couldn't be happier. Read Less