As another reviewer says, you get what you pay for. These are an incredible bargain if you want a cheap solution that will 'just do', but they're far from brilliant.
Mine turned up yesterday. Contrary to what some say, I did get 12 in the pack, however again turned up in just a jiffy bag with no instructions.
First one that I tried to put on was already cracked. And trying to get a good fit on it seems very difficult. Also have noticed they're slightly too short, and there is about 2-3mm of the iPhone's face that's not actually covered.
When I had my 4S I used to use the power support anti-glare ones, and they were fantastic, couldn't even notice that it was on.
These are fine, but I don't think I'll be sticking with them for long. If you want a dirt cheap solution, this is it. If you want something that will provide something slightly more, look elsewhere.