Features:

•Unlike a standard stereo connector, this actually has three conductors and a ground.
• Some devices use the extra conductor for a microphone (like hands-free headsets) or to carry a video signal (like in some MP3/MP4 players)
• If you’re hacking on something that has a 4-conductor audio jack, being able to plug straight in will keep your build clean and simple.
• 18″ Long (45.72 cm).