The lids fit perfectly on myPyrex bowls that didn't have lids.i have some liquidy foods for my lunch packs that I bring to work and it doesn't leak even after microwaving.
Update; Two of the lids ripped at the edges after a few months. I have to deduct 2 stars out of 5 because of this. Not very durable. Also it feels more like plastic compared to the rubbery feel of the original