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.

includes:

• Plug w/ solder-point connections
• Shroud to cover solder connections