Sennheiser PC 21-II Single-Sided Headset with Microphone Sennheiser sound Noise canceling clarity Reliable speech recognition Keep one ear free Fully flexible boom arm Noise canceling clarity - the microphone filters out ambient noise, so your voice is always clear and easy to understand Reliable speech recognition - the microphone is specially designed for your device's speech recognition function Keep one ear free - the single-sided design keeps you in touch with your surroundings Fully flexible boom arm - adjust the microphone for optimal voice pick-up and comfort Light and comfortable - with the lightweight headband, it's easy to forget you are even wearing a headset