This product is either discontinued or we cannot get that from suppliers.
Poly Plantronics Voyager 4210 214650-01, Voyager 4210 Headset, Wireless, Bluetooth, Over-the-head, Up to 12 hours talk time and 15 hours listen time, Up to 13 days standby time, Speaker range 20 Hz - 20 kHz, Speaker impedance 32 ohm, 360mAh typical/350mAh minimum, 1.5 hours for full charge.
The Plantronics Voyager 4210 UC is a wireless Bluetooth headset that is ideally built for UC applications and softphones and optimised for telecommunications, music, and media.