These fit very snug. Other brands had reviews that there were gaps in coverage, but not these. They fit tight to the outlet or switch and fill the back of the entire plate. If you have a double or triple light switch, trim a little off but leave some overlap for coverage.

Work pretty well, and great price. These seal up around the junction box itself but if there is any gap between the box and drywall the foam gasket probably isn't big enough to cover the gap. Smaller gasket size is understandable as the outlet cover sizes can vary. I combined these with some spray foam insulation at my junction boxes to really kill most of the drafts. Your mileage may vary.

Installed these on the exterior and interior walls. They were exactly what I wanted. The punch-outs are for the traditional switch that has a raised rectangle all around it. The vinyl wall plates bend a great deal and do not seal as well as the metal or plastic wall plates.

My 1960's house has metal electrical boxes with lots of holes inside and has gaps where the metal sides attach to the top and bottom metal. I bought low odor acrylic latex caulk and caulked the inside of all electrical boxes. I was never able to seal the inside completely, but it was much improved. I then replaced switches and receptacles as needed followed by applying the gasket cover to either the outlet or the cover.

Double and triple switch plates have the switches closer together so the foam gaskets must be trimmed. I used a utility knife for this task and then used caulk to attach the gasket to the back of the cover. In addition to saving on heating I hope that this also saves on the cost of humidifying. My inside switches did have dust in them so I know there is air flow where there shouldn't be. Be aware that the holes for the wiring (and plumbing) may not be sealed in the attic or crawl space.

Nice covers. I was amazed to see there were no gasket covers under any of my light switches and outlets. Once I installed these on the outside walls, we noticed a definite change in the temperature in the house.

I got these gasket covers not so much for insulation, but to try to decrease the amount of smoke coming into my apartment from neighbors who smoke inside. It did make somewhat of a difference, but I can still smell the smoke in my apartment. It's not going to completely block the smell, but I would recommend it to anyone who is desperate like me to try every little thing possible to stop the smoke smell! I also taped up any holes or crevices I could find on top of using these gaskets. They were very easy to install. Just need a screwdriver. If anything, I'll have some extra insulation in the winter.