Does the job
I bought one of these for the side grill of an antec 300. Although the frame of this filter is magnetic, I found that it didn't stay in place (it slowly slid down the panel) and I needed to get some cheap nuts and bolts to hold it in place. I guess this wouldn't be so much of a problem if a side fan was also fitted. Despite this, it does a good job of keeping the fluff out, has made the computer a bit quieter and hasn't affected running temperatures.