The Koss Plug revolutionized the world of in-ear headphones. A first of its kind, these are stereo, noise isolating in-ear headphones that deliver the kind of accurate acoustical reproduction and isolation typically found in high-end, closed-style high fidelity headphones. A dynamic element positioned just outside the ear connects to a tubular port structure that inserts into a soft, expandable cushion. The soft, foam cushion expands for a custom comfort fit with every listening experience. It also improves isolation, plugging out ambient sounds, and enhances deep bass and treble clarity. Combine the Koss Plug with your favorite music and it instantly becomes the ultimate accessory for on the go listening. Specifications: Frequency Range: 10 - 20,000 Hz, Impedantion: 16 Ohms, Sensitivity: 112 dB SPL/1mW, Straight, Dual Entry, 4ft cord. Finish: Blue