This product is either discontinued or we cannot get that from suppliers.
Poly Plantronics 85800-01, Blackwire, Headset USB, Talk time up to 10 hours (6 hours w/ A2DP), Speaker mono/single, Microphone boom arm, Voice quality wideband (up to 6,800 Hz), DSP, Inline Controls answer/end, volume, mute.
Plantronics C435/435 Blackwire UC Standard Headset is the first headset designed for Unified Communications that’s as discreet as it is professionally sound. Providing a choice of mono or stereo audio options and wearing styles.