On Ear Headphones. The acclaimed Koss Porta Pro has set performance and comfort standards for personal listening worldwide. Designed for those with refined musical taste, the Porta Pro continues to be one of the most popular headphones around the world. Known for its high-level of comfort, the Porta Pro has adjustable temporal pads to relieve pressure on the ears. Its lightweight, open-air cushions for hear-through sound keep listeners aware of their surroundings while delivering exceptional sound. The oxygen free copper voice coils and dynamic elements allow the Porta Pro to deliver rich bass and a remarkably wide frequency response. Whether you're listening at home or on the go, the Koss Porta Pro delivers all the excitement of a live performance. Specifications: Frequency range: 15-25,000 Hz, Impedance: 60 ohms, Sensitivity: 101dB SPL/1mW, Cable: Straight, Dual Entry, 4ft. Finish: Black