For what they are, a cheap pair of sunglasses, they're fine. There are however a few things you should note:
-One of the other reviews mentions that one of the arms was a bit stiff. Same with mine too. One was almost stuck in place while the other just flops around.
-Damn these things are dark! I mean sunglasses are supposed to be dark and all, but it's like I'm living in a black hole when I wear these things.
-The packaging the glasses were sent in was awful. It was just a lightly padded envelope. Flimsy sunglasses + lightly padded envelope + postal service = A pretty horrific sight. Both arms were bent at the hinges and the nose pads twisted and flat. Plus the left lens was coming out. Annoying yes, but after 5 minutes of bending they're easy to get back into shape.
I wouldn't buy these again, but they were only £4 so I'm not too bothered. However on saying that, I've bought better sunglasses for £2 off a market stall in the past.