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The lower end fram filters are reputed to be of very poor quality overall. I don't know if that is entirely true or not, but I don't recall ever seeing anyone tear them open or test them and dispute it.
The higher end fram filters seem to be better quality, but the reputation of the cheaper...
Here's a list of all the different filters that will work, and some are rated better than others
http://www.hummerknowledgebase.com/parts/list/005.html