Mx500i 3 In 1 Under The Head Hdst Sold as 1 EA. Versatile 3-in-1 design connects to your computer, cordless phone and most cell phones (requires a 2.5 mm jack). Ultra-lightweight, under-the-ear Flex Grip design for all-day use. WindSmart microphone technology reduces wind noise for enhanced call clarity. Adjustable one-touch volume controls and mute button.