Bests & Worsts Reviews from Amazon

I recently had a chance to install these in my own home. I have a single return that measures 12x24, on a 2 ton Package unit. I know that this will only allows for 600 cfm of the required 800 cfm the system needs to operate properly, I just haven’t gotten around to enlarging it yet. Now that, that’s out of the way.. in regards to the filters, they are properly rated as the air the travels through them will be filtered properly. Unfortunately as others have mentioned they are undersized for a 12x24 return grill. I was expecting them to be a little undersized, but they are very undersized. So undersized in fact that my return grill whistles now. The whistling is coming from the edges of the filter, which means air is passing around the filter and not being filtered at all, I will be removing these filters and installing something that fits snuggly, and doesn’t allow the air to pass around them. I’m really not sure what the thinking was when designing these, if the whole purpose of a filter is to filter ALL of the air that returns to the system, then the filter should fit properly. 12x24 is a common size, and the manufacturer should have known and tested there filters to make sure to size them properly. MERV 13 doesn’t mean anything if air can get around them. I’m fairly disappointed, I was excited about having great air filtration, since I just installed the system, this is a variable speed system, and the whistling was noticeable in low speed, I haven’t tested in high speed, but I imagine it will be even worse, based on experience.