Audicom Headset Adapter for 2.5mm Headset, RJ9/RJ10/RJ22 Headset Plug Adapter Converter for Yealink SIP-T19P T20P T21P T22P T26P T28P T32G T41P and Huawei ET325 ET525 Telephone IP Phones (H25-GXPC) Convert 2.5mm plug to single 4P4C RJ9/RJ10 headset or handset plug for your office phone Save money by buying standard phone headsets to use with your phone's headset jack Reduce clutter with single headset Does not work with RJ11 jack, which is wider than your handset or headset jack (6 positions vs. 4). RJ11 jack is what is in the wall. RJ9, RJ10, RJ22 are what is on your phone handset or headset. Only works for 2.5mm headset and some specific phones. Please see compatible phone models list in description below .ONLY BUY THE ITEM TODAY IF YOU HAVE ONE OF THE PHONE MODELS LISTED BELOW.