You've got a couple of options. IF you are only going to use it on one lens, i.e., one filter size, then most buy a screw in rotating polarizer or cpl. I like Hoya filters. They are more expensive, but good quality usually costs more. IF you want to use a polarizer on several different size lenses then you might want to buy a filter system like Kase, which is a well regarded system. Personally, I use the Lee filter system.
Just a sideways thought .... counterfeit Hoya filters abound from the cheapie sites
I had a student with one, and it had ripples within the glass and created a slightly fuzzy image too
I would make sure it's a 'goodie' when you get it