This RJ9 telephone headset with a noise-canceling microphone is specially designed for Cisco IP phones. It features with: Crystal clear soundWideband audio technologyAll-day wearing comfortHearing protectionQuick disconnect Noise Cancelling Microphone MKJ RJ9 headset with noise cancelling microphone reduce most of the background noise to let you to be heard clearly. Soft Ear Cushion With soft ear cushions, this wired headphone ensures all-day comfortable wearing even for long calls. Adjustable Headband The headband of headset can be easily adjusted to fit your head. Headset Compatibility (Included but not limited) Cisco 12 VIP, Cisco 30 VIP, Cisco 6841, 6851, 6921, 6921, 6945, 6961, 7821, 7841, 7861, Cisco 7931G, 7940, 7940G, 7941, 7941G, 7942G, 7945, 7945G, 7960, 7960G, 7961, 7961G, 7962G, 7965G, 7970, 7970G, 7971, 7971G, 7975, 7975G, 8811, 8841, 8845, 8851, 8861, 8865, 8941, 8945, 8945G, 8961, 9951, 9971, CTS500 Note: This RJ9 Cord ONLY Compatible with Cisco Phones with RJ9 Headset Jack!