Headband Pivots Backward At Its Base, Easily Converting From Over-The-Head Style To A Behind-The-Head Style Foam Ear Cushions Collapses Into A Compact, Protective Package That Tucks Neatly In A Briefcase, Gym Bag Or Backpack Freq Resp: 5 Hz-25 Khz 15 to 25,000 Hz frequency response Flexible headband design, fully collapsible Foam ear cushions for open sound Includes 0.125-inch and 0.25-inch stereo plugs Versatile headphones for any activity The Koss SportaPro portable headphones offer portability, flexibility, and a headband designed to be worn either atop or behind the head. Equally well suited for use at work or on a jogging trail, the SportaPro's open, foam-covered ear cups allow for ambient environmental sounds to be heard, which can be helpful in a recreational environment. The SportaPro's weight is a mere 2.2 ounces, and the headphones boast a frequency response of 15 to 25,000 Hz, delivering (on paper, at least) quite a bit more bass than most home speakers can. Impedance is 60 ohms, with less than a 0.2 percent distortion and sensitivity of 103 dB SPL (with a 1 mW signal). The SportaPro stereophones are collapsible and come with a carrying case, as well as both 0.125-inch and 0.25-inch jacks. Koss covers the headphones with a lifetime warranty.