I got a bunch of those dust filters for my Thermaltake case.
The nice thing about them is that it comes in TWO pieces, first piece is the one that gets attached to the fan by screws, the second piece holds the washable foam inside its frame and it "clicks" into the part that is attached to the fan, this way you can simply remove the top part to remove the foam and clean it, without having to go thru the hassle of removing screws and all that annoying stuff.
So far i have washed the foams of all the filters more than 4 times, and i vacuum clean them once every two weeks. I have been using them since March 2008 and so far they didn't show any wear-n-tear. Two thumbs up for foam quality.
The not-so-nice thing about this filter is that since it is made of two parts, and the top part sits on top of the attached-to-the-fan part, the top part is a bit bigger than the base, and i have two fans at the bottom of my case that are next to each other, therefore the two filters can't "click" into position from the side where they are next to each other. Fortunately, they are snugly fit from the other 3 sides to stay put and not drop down off the base even tho the filters are FACING DOWN from the bottom of the case. This has cost them 1 star.
Still i highly recommend this product for its excellent quality.