This product is either discontinued or we cannot get that from suppliers.
Poly Plantronics Bt300-m Uc Bt Usb Adapter 85117-02, External, Interface (Bus) USB, Connectivity Wireless, Bluetooth 2.0, Max Range Indoors 33 ft, Connections 1 x USB - 4 pin USB Type A.
The Plantronics BT300 Bluetooth USB Adapter adds computer connectivity to your existing Plantronics Bluetooth headset. It is compatible with the Plantronics Voyager Legend UC and Voyager Pro UC series headsets and is optimized for use with Unified Communications.