The PH25-RJ9Cisco converts the standard phone headset 2.5mm plug to a standard RJ9, RJ10, or RJ22 Cisco phone headset plug, allowing you to use your favorite phone headset with your Cisco office phone.Use the Headset Buddy Adapter and your existing 2.5mm phone headset with Cisco VOIP phones that have a headset jack. Save money by using a 2.5mm headset with your Cisco office phone.The adapter cable is approximately five inches long.