Are you talking about the outer rim of the lid? I have two bucket fermenters and one has one, the other doesn't. The one without seals just fine, the lid seats nice and snug. If you want to test it, just snap the lid on tight, put the airlock with liquid in it into the hole in the lid, and then press down with some pressure on the center of the lid. If the airlock bubbles, you have a seal. If not it leaks.