Universal Premium Mono 2.5mm Hands-Free Headset with Boom Microphone for landline phone, cordless phone, office phones, business phones Cellet Universal Mono 2.5mm Hands-Free Headset with Boom Microphone. Reduces Background voice: Comfortable ear speaker providing clear sound quality and can be worn on right or left ear. Blocks out unwanted background noise in the office or call center. Strong and durable 6.56 foot long cord with leather cushion ear is made to last multiple uses. Great for using at call centers. Inline control, it allows you to activate your smartphone, personal voice assistant, play/pause/skip music and answer/hang up phone calls. Built To Last: Compatible to 99% of office phones. Featuring a heavy duty adjustable headband and flexible boom microphone, the headset can accommodate various head sizes and desired angles.