Wantek Mono Call Center Headset with Mic + Volume Mute Controls for Cisco Linksys CIT200 CIT300 SPA921 SPA922 Grandstream GXP-2010 GXP-2020 GXP-2100 Telephones with 2.5mm Headphone Jack(H110S04J25) Only works for some specific phones with 2.5mm standard headset Port. SEE COMPATIBLE PHONE LIST IN DESCRIPTION, BUY THE ITEM ONLY IF YOU HAVE ONE OF THE PHONE MODELS LISTED BELOW. 2.5mm Jack Direct connect headband telephone headset headphone, No additional amplifiers or adapters required. Superior Call Center quality sound headset with flexible adjustable noise canceling microphone. Super Lightweight, Super Durable Headset with Comfortable ear and mic cushions for all day use. With Mic Mute / Volume Control built in.