"We celebrate the 25th anniversary of the Koss Porta Pro with this special limited edition model to commemorate the vision and leadership of our founder John C. Koss and the development of the sound heard ‘round the world: The Sound of Koss. The Porta Pro 25th Anniversary Limited Edition features dynamic elements that deliver exceptionally rich, deep bass and a remarkably wide frequency response from 15-25,000 Hz to capture every nuance in your favorite movie or musical performance. Constructed from mylar, the elements are extremely rigid, minimizing mechanical distortion and ensuring exceedingly accurate sound reproduction. Neodymium iron boron rare earth magnet structures enable the Porta Pro 25th Anniversary Limited Edition to deliver greater volume so you can hear every note, even when competing against the sounds of a commuter train with a low-voltage MP3 or disc player. Oxygen free copper voice coils improve signal transmission and conduction for cleaner, clearer sound. Foam ear cushions provide an open, hear-through sound that lets you keep in touch with your surroundings perfect to wear while running, at work, or while traveling. Whether you’re listening at home or on the go, the Porta Pro 25th Anniversary Limited Edition will bring the excitement of a live performance to any recording. The PortaPro by Koss is covered by Koss' No Questions Asked Lifetime Warranty."