I have a number of cloth and paper masks, all of which 'leak' and cause my glasses to fog. I own and have tried several respirator type masks, like the Gill Mask. But the Gill Mask is my favorite, by far. And the Pro is even better than their original. Both versions give me a good tight seal, but are comfortable to wear for long periods and my glasses don't fog. The Gill Mask Pro does make breathing much easier.
I have already recommended this mask to others and continue to do so.