The KDX100 ear bud is a versatile stereo phone designed with comfort and sound production in mind. It delivers accurate acoustical reproduction and unbelievable isolation typically found in more expensive, closed-style stereo phones.The KDX100 features a dynamic element that is positioned just outside the ear and connected to a tubular port structure that is inserted on one of two provided cushions: a fluted silicone or conforming memory foam cushion. The fluted silicone cushion provides a firm, flexible seal while the soft foam cushion expands for a custom fit to improve isolation and enhance deep bass and treble clarity. The custom fit enhances isolation when you want to plug out ambient sounds that interfere with the listening experience. The KDX100 has a frequency response performance of 10-20,000 Hz and full sound of Koss. Combined with your favorite music and a portable sound system, it is the ultimate accessory on the go.