Instruct: Classify Amazon reviews into positive or negative sentiment
Query: For $30, I thought I knew what I was getting

I bought this today as an alternative to more expensive polarizers. I figured, yeah, it's not going to perform as well, but it should be good enough. I was wrong.The problems start before you even put this on your lens. That is, if you can get it on your lens. The threading sucks, and even at its tightest, mine never screws on flush with the lens barrel and always feels loose.The threading on the outside is short, too. I prefer to put my polarizers under my UV filters to protect them, but this one won't hold it. Similarly, I can't even put my Canon lens cap over the polarizer if it's on the outside because the threading is too short to hold the clamps.Now on to performance. What performance? Done.I feel dirty for even letting myself buy such a cheap filter.