The single-earpiece design utilizes our special 1-Ear technology to mix the left and right audio channels together, so you hear both stereo channels mixed into a single earbud. This is particularly helpful for those who have single-sided hearing or deafness in their left ear, and can only hear in their right ear. It is also quite useful for those who hear in both ears, because it allows you to keep your left ear open to hear what is going on around you. The single-ear earbud design is required now by many employers who will only permit employees to listen to sound in one ear if they are at work.