This product is either discontinued or we cannot get that from suppliers.
Poly Plantronics Bt300-m Uc Bt Usb Adapter 85117-01, External, Interface (Bus) Type USB, Connectivity Wireless, Bluetooth 2.0, Max Range Indoors 33 ft, Connections 1 x USB - 4 pin USB Type A.
The Plantronics BT300-M Bluetooth USB Adapter adds computer connectivity to your existing Plantronics Bluetooth headset. It is compatible with the Plantronics Voyager Legend UC and Voyager.