【Not for Cell Phones and Computers】: ONLY COMPATIBLE with some Specific Phone Models from Plantronics Polycom Avaya NEC Toshiba Shoretel Mitel Allworx Zultys Nortel Aastra InterTel Siemens Digium and etc. Callez phone headset works for Polycom: SoundPoint 300 301 335 430 450 500 501 550 600 601 650 670 CX300 CX500 CX600 CX700 VVX101 VVX201 VVX301 VVX300 VVX310 VVX400 VVX410 VVX411 VVX500 VVX600 VVX1500. | CRYSTAL CLEAR CALLS: Wideband corded telephone headset offers excellent sound quality for natural listening experience, features Noise Cancelling Microphone to reduce background noise, plus Acoustic Shock Protection protects our hearing. Less noise, Clearer voice. | MOST COMFORTABLE HEADSET: Ultra lightweight RJ9 landline phone headset designed with adjustable headband fits all head sizes, a flexible boom mic suits your preference, soft and high quality leatherette ear cushion enhances all-day wearing comfort. Feel no burden during long-time work. | ULTRA DURABLE HEADSET: Precision design, quality plastics, uni-body headband construction, flexible metal mic boom make this RJ9 call center telephone headset more durable and sturdier. Compete with Plantronics or Jabra business-grade phone headset. | WARRANTY GYARANTEE: We offer 45 days money back & 24-month worry-free guarantee for our all office phone headset. Ideal for Counselling Service, Insurance, Hospital, Call Center and more. Buy the item today ONLY if you have one of phone models in list. For other phones, pls contact us for Compatibility Guide or Advice.