TRS connectors are the audio-style connectors that you see on some phones, MP3 players and development boards. TRS stands for "Tip, Ring, Sleeve." If you're hacking on something that has a three-conductor audio jack, being able to plug straight in will keep your build clean and simple.
Note: This plug allows you to add a custom length of wire to your connector or repair a broken shroud on an existing cable you just cannot live without. Unfortunately, the supplier has not provided a datasheet or dimensional drawing please see the similar documents provided by other SparkFun products on the "documents" tab.
Based on 1 ratings:
Knocking off one star (should only be 1/2) for the lack of an integrated bend relief, but you can slip some heavy heat-shrink over your cable to get a little added protection where it exits.
It necks down right before the 3.5mm jack so it fit into phone cases well. It was actually easier to solder to than it looked. I just fanned the strands and tacked them directly onto the metal surfaces.
I didn't completely trust the outer shell not to unscrew over time, so I put a bunch of silicone glue inside. That should pot the solder joints a bit as well. If you don't have glue or sealant around, you can use nothing, or perhaps put some loctite on the threads.