Sennheiser Remanufactured HDC-451 NoiseGard Noise-Canceling Headphone Noise-canceling headphones ideal for blocking out background engine noise or other distractions NoiseGard active noise compensation reduces ambient noise by up to 10 decibels 20 Hz to 18 kHz frequency response; total harmonic distortion of less than 1 percent Includes 1/4-inch stereo and 2x mono adapters; weighs 0.25 pounds (without cable) Remanufactured to like-new condition; 90-day warranty