The KSC9 uses an electro/dynamic element that delivers a frequency response of 40Hz-20,000Hz. Intra-aural, or inside the ear, earbuds have been turned sideways to aim the sound directly into your ear canal for surprisingly awesome sound and kicking bass. The side firing design naturally projects the sound to your ear and also reduces the amount of physical contact to make the stereophones more comfortable. The vertical side firing design is the least isolating allowing some sound into your ear without compromising the sound quality. This innovation allows the listener to remain aware of important outside sounds while enjoying the Sound of Koss. The KSC9 is big in sound, yet small in size, which allows you to store it anywhere from your pocket, briefcase or purse. The KSC9 features a pliable molded rubber ear clips that fit directly over the ear. Designed for maximum comfort, this clip eliminates the need for a conventional headband, but fits securely enough in your ear so you can also comfortably wear the KSC9 while active and on-the-go. The 3.5mm L-shaped plug reduces strain on the cord, meaning it will last longer no matter how many times you plug it in or unplug it. Built to last, the KSC9 is covered for the lifetime of the user under Koss’ No-Questions-Asked Lifetime Warranty – the only warranty of its kind in the stereophone industry.