This product is either discontinued or we cannot get that from suppliers.
Poly Plantronics Encorepro 203444-01, Headset - wired - USB, Use Phone, computer, Microphone Boom, Sound Output Mode Stereo, Controls Mute, volume, answer/end.
Plantronics EncorePro HW525 USB is a stereo PC USB headset compatible with all major softphones (Avaya Cisco, Microsoft Skype for Business, etc).