Filterbuy 21x21x4 Air Filter MERV 11 Allergen Defense (4-Pack), Pleated HVAC AC Furnace Air Filters Replacement (Actual Size: 20.50 x 20.50 x 3.75 Inches)

I received four filters with my initial order. The four filters arrived in a thin shipping box that was damaged including the four filters contained inside which I returned for a replacement. The second order arrived in a thin box and this time the shipping box and the filters inside were not damaged. I examined the four undamaged filters. I discovered that the filter insert on all four filters was not attached to the four sides of the box structure. The filter insert was only attached on two sides. This allow for unfiltered air to pass through the sides of the filter insert that is not attached to the sides of the box structure. In addition, the box structure containing the filter insert is composed of thin cardboard which bends easily and damages easily on handling.

What follows also applies to AFB Gold MERV 11 14x14x1 Pleated AC Furnace Air Filter. Pack of 4 Filters. These filters look to be well made and filter well. My primary complaint is that they don't fit well in the filter grate openings. Prior to using these filters I used the Filtrete 3M brand sold at the local Lowe's. The 18x30 and 14x14 Filtrete filters fit snugly in the grate opening while the AFB filters are slightly smaller that the advertised dimensions. What does this cause you might ask? The answer is: the AFB filters make a "thunk" sound when the AC shuts off as the filter falls out of the opening and onto the grate door. Occasionally we'll also get a "whistling" noise when the AC starts up as the AFB filter sucks back up in the grate opening, but the alignment is slightly off. I managed to solve these problems by using small foam blocks at the corners of the grate door such that they push up against the AFB filter and prevent it from being noisy. I never had the problem with the Filtrete brand so I'll be going back to them when I use up the AFBs.

We have 4 cats, yet this filter model takes care of keeping the air handling equipment clean and operational. We're also in the desert and have had no problems with dust or seasonal pollens. All the vents have remained clear of any build-up, as it should be if everything is working correctly. These filters last us more than 3 months, though I try to remember to change them every 3 months as designated. We've been using this type for almost 2 years and have been very satisfied.

These filters are actually 19.5 X 29.5. No big deal huh? Yes it is a big deal you're installing it overhead and the proper sized filter or even one 1/4" larger will catch on the little protrusions so that you can close the cover without it falling on you. I know the dimensions are listed, I know some reviewers mentioned it but since the ones that were in there were undersized I figured these would work fine, not so. However with a little Yankee ingenuity I managed to get it installed. Don't know how they will work, don't care, I won't be buying them again. I don't need the aggravation and for the life of me I can't understand why manufacturers do things like this. If you're going to sell a 20x30x1 furnace filter, make the darn thing 20x30x1. I'd send them back if it wasn't such a pain.

It's a half inch smaller than the advertised dimensions. It keeps falling out of the slot in my AC duct. I've had to tape extra cardboard to the side to get it to stay in. This should have been made crystal clear in the ad.... I ordered from my phone and saw nothing about the dimensions being so much smaller than advertised (I know all AC filters are a bit smaller, but this is ridiculous). will stay with my usual brand next time (which fit fine!).

I am very happy with this purchase. Not only is it less expensive, but it is actually more quiet than the other filters I have purchased at the local "home improvement" store. Why, you ask? Because it actually fits! You see, when the filter does not fit properly there is additional airflow that goes around the filter creating a sort of whirring noise, not to mention the sound of the filter being sucked up and dropping when the cycle starts and finishes. These filters fit perfectly and the noise level has noticeably dropped. I have only had the filter in for about a week, so I cannot comment on how they are over the long term, but the noise reduction alone will likely keep me purchasing from this supplier.

Since most local stores don't carry this size I looked to Amazon and they had this one. Overall it's a good filter and I like the higher MERV rating. Air quality upstairs has improved but it is noticeable louder when the fan is running - probably due to the denser pleats. My three main knocks against it is that it's a bit shorter than advertised by about 1/4" inch all around so it's not a snug fit. All four of the filters arrived slightly dented - they weren't unusable but seems like the packaging or handling prior to shipment was poor. Plus the description and product image shows white pleats and what arrived was yellow. Either Amazon or the company needs to update the item picture with what actually ships.

I am writing this after I discovered a weird sound emanating from my HVAC. Upon closer inspection, my HVAC was working very hard in trying to get air to flow. It turns out the air filter was severely restricting air flow to the point where pulling the air filter out resulted in the frame of the filter tearing due to the strong suction of the HVAC. This is not MERV-11 behavior. And this is not a case of I neglected to change my filters. I am keen on I would rather change sooner rather than later. Buyer beware. Pay close attention to your HVAC performance as it's my impression the particular filter I put in made by FilterBuy was not porous enough to sufficiently provide MERV-11 airflow. The savings are not worth the risk of having to replace an HVAC system.