BTunes M50x Bluetooth Connector review
The Bluetooth adapter costs about $55, when I purchased it from Amazon.com. it comes with a short micro USB charging cable and a user manual in the packaging. Battery is fully charged from factory.
It has a snappy connector, so it slots into the M50x headphones, making a satisfying click sound in the process. Removing it requires a little force, so it won't fall off by itself.
In terms of sound quality, it's no different to having a wired connection. Which is a good thing. I felt no loss of quality using wireless connection.
It supports voice calling, HD Audio etc. However, the microphone is not very good and picks up a lot of background noise. So I don't use it for calling.
The battery life is also good. It charges up using a micro USB connection in about 2 hours. When full, it gives about 8 hours of playback.
It also comes with auto Power Off. Once the Bluetooth connection is disconnected, it powers off itself after a short while. Which is a good thing for battery life.