I have to take back everything I said in this review I posted shortly after the order came.
They are in fact stereo, I'm not sure why when I first tested the windows playback that both headphones were playing both R and L sound, but I decided to give them another try (Not sure why even! just on a whim) and :O they're working.
I have to admit the possibility is that I didn't push my headphones in properly the first time.
Either way, here's the important part: They work. They successfully take the stereo signal and double it, sending two stereo signals out - one out each socket meaning you care share music with with your mates without any loss of sound quality.
I personally have mine connected to the tv, then to two wireless headsets which enables me and my friend to watch loud action movies way into the night without disturbing any of the neighbours. Top stuff!