A couple questions for those of you that have used Gamma Seals.
Do they fit on drywall mud buckets?
I have read other threads that recommend a rubber mallet for installation. Once on, do they come off again with no damage?

I use them on 5 gallon pails. They don't fit all pails, but most. Some pails have a lip about 1/2" from the top, they don't fit those because the lip interferes with seating the outer ring. In my experience they fit Lowe's 5 gallon pails better than Home Depot's. I don't have any experience with the square ones.

They fit on most 5 gallon pails. You just hammer on a plastic rim that has the threads with a rubber dead blow hammer. Then the top just screws on to make the seal. The access lid is a separate part that screws into the rim that you pounded on the bucket. They screw on and off pretty easily. I’ve never tried to remove it totally back off. At home they work for dog food, bird food, cat food. Then when it’s trip time, just clean them out.

once on I doubt you can get them off without damaging them. The Gamma Lids also fit the 5 1/2, 6, 6 1/2 and 7 Gallon buckets as well. You can find the larger volume buckets in the home brewing stores typically. they will fit the dry wall buckets- if the lip of the bucket is damaged they can leak.

A brand new bucket is 1/2 the of the cost of the lid. They will be permanently mated so, a new bucket seems a reasonable choice.

I was able to remove the collar without damage. I first removed the lid. Warmed bucket by placing it in sun. Placed it on its side and began gently tapping it with a wood block and hammer as you rotate the bucket. It may take several revolutions as you slowly work it off. It wasn’t damaged at all.