erm, in my opinion this also applies to the USB-BT adapter that comes with the headset (which was so stupidly included in the package that I almost threw it away with the box). The older models had a USB-A - Bluetooth plug, the newer ones a USB-C. You don't necessarily need the BT adapter, you can also pair the headset directly with your devices, but with the BT adapter from Poly you can be connected to the headset on your laptop and your mobile at the same time, for example. This should make it possible to listen to music and still be able to take a call, for example. For me, however, toggling doesn't always work so well.