I have the best made coffee (thermos) mug in the world. Highly recommend the Thermos King! The lid is leakproof! Unless you forget to close it. So, the side pocket in my Cafe Bag is now holding about one cup of coffee! Oh no! I have valuable papers in the bag. Guess what? The coffee did not leak into the bag! I didn't know the material was leakproof. Or at least water resistant. Yes, I need to wash the bag, but WOW! I thought I was a goner!