KOSS Headphones PortaPro On Ear, The ultra portable on-ear headphones, Comfort Zone setting for comfortable secure fit, The ultimate active headphone with folding headband, Dynamic element for extended frequency response, Oxygen-free copper voice coils deliver deep bass and clear sound, Includes a convenient carrying case, Limited Lifetime Warranty, The world's most beloved headphone - a classic since 1984. Well-known headphone that is found in the top tier in tests year after year. Koss Porta Pro has dynamic elements, and ComfortZone setting for the best fit. The headphones are foldable for protection during transport or storage. Specifications, Impedance: 60ohms, Frequency response: 15 Hz - 25,000 Hz, Cord Length: 115 cm, Plug: L-shaped, gold-plated stereo plug 3.5mm.