KSC21 The KSC21 Stereophone delivers a wide range frequency response while clipping comfortably over the ear. Soft, foam ear cushions guarantee an open, hear-through sound-perfect when you want to stay connected to your surroundings. Pivoting earplates provide a better fit than most clips. The KSC21 features dynamic elements for an extended frequency response from 50-18,000 Hz. Oxygen-free copper voice coils improve signal transmission and conduction for cleaner, clearer sound. Perfect for travel, the KSC21 includes a straight dual-entry four-foot cord, and a 3.5mm (1/8") plug. Built to last, the KSC21 is covered under Koss’ Limited Lifetime Warranty - the only warranty of its kind in the stereophone industry. Specifications Frequency Response 50 - 18,000 Hz Impedance 36 ohms Sensitivity 101 dB SPL Distortion Cord Straight, Dual Entry, 4ft