Comdio H303VP1 2.5mm Call Center Headset Headphone with Mic + Volume Mute Controls for Cisco Linksys SPA SPA921 SPA922 SPA941 SPA942 SPA962 303 501G 502G 504G 508G 509G 525G Telephone IP Phones ONLY WORKS FOR SOME SPECIFIC PHONES WITH STANDARD 2.5MM HEADSET JACK. SEE COMPATIBLE PHONE LIST IN DESCRIPTION, DO NOT BUY THE ITEM IF YOU DO NOT HAVE ONE OF THE PHONE MODELS LISTED BELOW. Superior quality sound with the flexible adjustable noise cancellation microphone. Super Lightweight, Super Durable Headset with Comfortable ear and mic cushions. Direct connect over the head headset headphone, No additional amplifiers or adapters required, Most easy setup headset solution. In-line Mic Mute / Volume Control built in.