Was supposed to split a single earphone with built-in mic to two different connectors for use with a PC.
Be aware that there are no standards for those connectors, so different earphones might have different results.
I tested with both Nokia and Samsung phone original headset. There is an issue with the order of the connections on the earphone connector.
With Nokia, mic was not working and the audio sounded horrible.
With Samsung, it worked.
Be aware that if you have Jack Sensing in your PC, it might not work properly (keeps detecting connects and disconnects, causing sound the break).
I bought 5 of these because I wasn't aware of that.