I wasn't planning on putting the small one's on the filter covers, but I had the covers in the house where it was warm to put the big one's on. These covers aren't a perfect rectangle, I was being so careful to get the right measurements to get centered on them and I screwed up and forgot to deduct a 1/2" from one side witch put them off center. Sooo I thought I'd put the small one's on there so it looked like "I meant to do that".