Call Center Headset Headphones + Adjustable Volume + Mute Control For MITEL Phone Superset 4000 Series, Mitel 5000 IP Series, Mitel 5200 502Xi IP Series, Mitel 5220 5230 Series Ip Telephone. Direct connect over the head headset, no additional amplifiers or adapters required. Built-in adjustable volume and mute control. Soft leathered ear cushions for all day comfort. Superior quality sound with the flexible adjustable microphone. Comfortable lightweight design, shirt clips included.