4Call K500QMC Corded RJ Telephone Headset QD with Noise Canceling Mic & VC for Aastra Shoretel Nortel Cisco E20 Polycom 335 VVX400 Digium D40 D70 Altigen 500 720 Comdial & Starleaf Office IP Phones WORKS ONLY FOR PHONES LISTED IN DESCRIPTION, BUY ONLY WHEN YOU HAVE ONE OF THE PHONES LISTED. CONTACT US FOR GUIDE IF YOU ARE NOT SURE ABOUT YOUR PHONE COMPATIBILITY. NOT COMPATIBLE WITH CISCO SPA PHONE SERIES! Direct connect headset, no additional amplifier or adapter required. Adjustable fit headband and comfortable ear cushions enhance for wearing comfort, even for long periods. Single earpiece with noise canceling microphone for superior sound pick up even in noisy offices. The single earpiece means you can still confer with colleagues while you're wearing it Flexible microphone boom, 270 degree rotatable, which adjusts to suit your preference, you can also choose to wear the microphone on either your right or left side. Quick disconnect feature enables you to disconnect quickly from the bottom half the cable, while still wearing the headset. With Mute / Volume Control built in.