Plantronics - CS540 Wireless DECT Headset (Poly) - Single Ear (Mono) Convertible (3 Wearing Styles) - Connects to Desk Phone - Noise Canceling Microphone. Global Warranty & Wearing Style: 2 years; monoaural light weight convertible (which can be worn either over-the-ear, over-the-head or behind-the-head).