THERMWELL Frost King AC43H Air Conditioner Weatherseal Tape, 2-1/4 by 2-1/4 by 42-Inch

The THERMWELL Frost King AC43H Air Conditioner Weatherseal Tape is a simple but highly effective solution for sealing window AC units and eliminating the drafts, vibration noise, and dust gaps that tend to show up around older installations. The foam is dense enough to provide a firm, reliable seal, yet still compresses easily to fit uneven gaps without tearing or crumbling. At 2‑1/4 by 2‑1/4 inches and 42 inches long, the size is generous and works well for both side and top gaps on standard window units. During installation, the adhesive held securely without needing reinforcement, and once in place, the foam stayed put even through temperature swings and daily AC vibration. The material also rebounds well, maintaining its shape rather than flattening out over time. For anyone installing a new unit or tightening up an existing one, this weatherseal tape offers dependable performance, easy handling, and a noticeable improvement in insulation and noise reduction.

I purchased this to fill the space between two windowpanes in a side-to-side sliding window after installing a window air conditioner. There was about an inch of space between the panes in a high wind area with typical winds of 20mph and frequent 30mph gusts in normal weather conditions. Everything I tried quite literally blew right out of place. I decided to give this a try and ordered the 2-1/4 inch size, so that I had plenty of room to squish it down and let it expand into place. It worked great! It was easy to install. I just pressed it down as sliding into place a little at a time and then adjusted it to make sure it was straight and aligned with the window to ensure it looks nice. The foam is sturdy, yet easy to squish to install. It took less than 5 minutes to seal both window spaces inside and outside. It expanded into place and is tightly packed. The winds (and dirt they bring) don't stand a chance!

Arrived as stated and does the job I bought it for. I use these for around my window a/c unit but I also live in a VERY old apt that has many cracks! These can be cut easily for use in sealing cracks around old windows in conjunction with the plastic I also use and these work wonderfully. Easy to install and I suggest the grey. Good quality! Good packaging! Great seller! Recommend!!

First let me address this saying this is not TAPE. There is no sticky adhesion on it, nothing like a 3m tape that you remove some plastic and stick it on. This is just a foam strip. With that being said.... Its a GREAT one ! Perfect for that gap at the bottom of the air conditioner. Its too thick for the gap at the top of the open window but it is PERFECT for the large gap under the air conditioner. The weight of the unit compresses it and blocks all possible gaps.

Reliable Seal, Easy Fix 🧊🛠️ THERMWELL Frost King AC43H delivers a snug, secure seal for window AC units. It’s easy to apply, holds up well, and keeps drafts out—perfect for boosting efficiency without hassle.

This stuff works well to stop the flow of heat out of a hot water register. I have hot water heat and one of the rooms is between heated walls. It doesn't need much heat. So I closed it off by stuffing the foam under the register. There is no fire danger because the water flowing in the register pipe is max 180 degrees.

This product is exactly what I was looking for to stuff around my window AC Unit! Be aware that it is extremely thick, but it can be cut very easily with a utility knife. It is a pretty thick material also, not thin and flimsy like some brands.

Easy to use, compresses well during install. Does its job, but lasts only a season or two. Dries out and crumbles.