RJ9 Phone Headset Compatibility: MKJ wired headphone with RJ9 jack is compatible with most landline phones, including AVAYA 1408, 1416, 2410, 2420, 4610, 4620, 4621, 4622, 4625, 4630, 5410, 5420, 5610, 5620, 5621, 5625, 9404, 9406, 9408, 9504, 9508 Aastra 480i, 53i, 55i, 57i, 57iCT, 6725i,6753i, 6755i, 6757i, 8004, 8009, 8314, 8324, 9009, 9216, 9112i, 9133i, 9143i, 9316cw, 9417cw, 9480i AudioCodes 405HD, 420HD, 430HD Polycom 300 320 Altigen Gigaset Fanvil X5 series etc. High Efficiency: Professional phone headset with microphone enables users to deal with computer tasks or keep notes while on the phone calls. Also you will get away from the neck pain caused by holding the handsets. HIGH DURABILITY: In spite of the crystal sound and wearing comfort, MKJ call center headsets for landline phones also focus on the great durablity of headsets to ensure that they are with lasting performance. MKJ phone headsets are made of high quality materials (top quality PU and plastic parts, reinforced cord) and exquisite workmanship to withstands the tough environments. All-day Comfort: The office headset weight is 70g only, very lightweight and comes with soft ear cushions to ensure all-day use in busy call centers, telemarketing offices, remote home offices... Crystal Clear Chat: This RJ9 telephone headset for desk phone comes with a superior noise cancelling microphone and dual ear design enable you to hear and to be heard clearly. The noise cancelling microphone picks up loud and clear voice for clear conversation, and the two ear headsets help you focus on the conversation.