It's the remains of the ball of Wendy Roam Fusion sock yarn I used to make this pair of plain socks.
Here they are:
I have to say that it's not a yarn I'll be buying again. It's quite loosely plyed, which meant it was easy to split it whilst knitting (a bit more twist would have made a difference). It's also not that soft. The finished socks feel a bit rough and also a bit hairy. Once I've worn them and get round to washing them, I might rinse them in some water to which I've added a blob of hair conditioner and see if that softens them up again.
Having said that, I'll probably find that these wear like iron and I'm still pulling them on my feet two years from now!