This lid worked fine for my 6.5 gallon fermenter bucket. It seemed to have a nice seal, with a rubber gasket embedded in the lid. Opening the lid was a bit easier than getting it on, working my way around the perimeter and pulling up the edges about 1/6 turn at a time.
The only things that detracted from it were the airlock positioning. Half the time, when attempting to remove the airlock, I pulled the little red seal out instead and had to re-instert it in the hole. I am somewhat concerned about the fit and longevity of the seal based upon this. The other (very minor) thing is that the placement of the hole on the lid close to the perimeter results in the airlock wanting to sit in there a bit crooked, about 10-15 degrees. Maybe that helps with off-gassing: not sure.
Anyway....it worked very well, so I don't have any major complaints.