3" EMT Knockout Cover

I needed a knockout seal for a 3-inch EMT conduit hole in a giant fuse panel. Come to find out, they basically don't exist. So I improvised this to use with a 4" plumbing cleanout access cover, Sioux Chief part number 870-4PK1. It may not be to code, but it's better than nothing. The hole prints threaded for 1/4-20, I did run a tap through mine, but it's probably not necessary. As designed, this will fit a knockout hole diameter of minimum 90mm. I used PLA+.