Sleek and lightweight, the GN 2110 SoundTube uses Acoustic Transmission Line (ATL) technology?the first significant advancement in voice tube technology and design. GN Netcom?s ATL technology eliminates sound reverberations and distortions usually associated with plastic voice tubes. It's lightweight, very durable, and extremely comfortable, even if worn all day long. A click-stop headband provides a customized fit and pillow-soft ear cushions rest gently over the ear. This model is a monaural headset (you hear through one ear), and the 2115 is binaural (two ears) -- which improves audibility of weak voices and blocks out distracting ambient sounds and nearby voices.