Bluez 2 are bone conduction headphones from Aftershokz. They u | Trend wave

Bluez 2 are bone conduction headphones from Aftershokz. They use technology to transmit sound through the bone to the inner ear. This leaves your ears completely free to hear everything going on around you.

But when you use the headphones during calls, noise cancellation is turned on, allowing the person you are talking to to hear you better, even with external noise on your side.