HP Poly CS540 Wireless Convertible 3 in 1 HeadsetEveryone in the office could use more flexibility. Let them roam confidently up to 400 ft from the headset base. Theyll be able to collaborate simply since teams can conference up to four headsets on a single base. Theres more than one way to make a call switch up styles to find your groove and introduce your ears to something new. The CS540 convertible design comes with three wearing options: over the ear, over the head, behind the head .