WARRANTY GUARANTEE: 45 days money back & 24-month worry-free guarantee for our cisco phone headset. Buy the item ONLY if you have one of phone models in list. For other phones, pls contact us for Compatibility Guide or Advice. Ideal for Counselling Services, Call Center, Home and Office. MOST COMFORTABLE HEADSET: Ultra lightweight office phone headset with adjustable headband to fit most head sizes, a flexible boom mic picks up your voice clearly and soft leatherette ear cushion enhances all-day wearing comfort. Feel no burden during long-time work. DELIVER CRYSTAL CLEAR CALLS: Corded RJ9 phone headset for Cisco phones with noise cancelling microphone filters out background noise and provides the crystal clear sound quality. Wideband audio delivers clearer conversations, while Acoustic Shock Protection protects our hearing. RJ9 HEADSET COMPATIBILITY: ?Not for Cell Phones and Computers?this telephone headset ONLY works for some specific CISCO phone models listed above, NOT for Cisco SPA series and Cisco 7902, 7905, 7905G, 7906G, 7910, 7910+SW 7911, 7912 IP Phones. For other phone models, please contact us for Compatibility Guide or Advice. ONLY COMPATIBLE WITH CISCO IP PHONES: this phone headset perfectly fits for Cisco 7931G, 7940, 7940G, 7941, 7941G, 7942, 7942G, 7945, 7945G, 7960, 7960G, 7961, 7961G, 7962, 7962G, 7965, 7965G, 7970, 7970G, 7971, 7971G, 7975, 7975G, 6821, 6841, 6851, 6921, 6941, 6945, 6961, 7811, 7821, 7841, 7861, 8811, 8841, 8845, 8851, 8861, 8941, 8945, 8961, 9951, 9971.