Dual Headset Headphones with Volume+Mute Control+Standard 2.5mm+Noise Cancellation Mic for Cisco SPA Series Spa303 Spa504g, Polycom Soundpoint Ip 330, Grandstream, Linksys, Panasonic, Cortelco Dual headphones+Noise canceling microphone to reduce background Noise Built-In Adjustable Volume + Mute Control Superior Quality Sound with Flexible Adjustable Microphone FREE Extra Leathered Ear Cushion Cover + Cover for Microphone Please see compatible list in description