They are great for the price, i have never had any problems with the 8 dollar one. And it has been dropped several times and survived unlike many others. Also it is very strong compared to the ones ive tried.
Next week I will be getting a new PK ring since mine no longer fits well. Once I get the new one i will give the old one away to anyone who needs it, for free. I see no reason to keep it. So if you are a size 8 and are interested, let me know.