Review on Chilly's Bottles - Leak-Proof, No Sweating, BPA-Free Stainless Steel Water Bottle - Reusable, Double Walled Vacuum Insulated - Keeps Cold for 24+ Hours, Hot for 12 Hours by Johnny Black

We've had these mugs for several months with no problems. They seemed wonderful, well insulated, easy to use. However, a few weeks ago we noticed the smell of mold and mildew in the cups. We disinfect, wash, regularly clean under the O-ring and run them in the dishwasher. However, nothing gets rid of the smell of mold and mildew. It turns out that the lid has seams, the stopper that screws onto the cup. The seams allow water to enter the cup lid, which screws onto the cup. This keeps mold and mildew out and there is no way to take this cover apart to clean the inside. This is obviously a serious design flaw and not an accident like what happened with both mugs we have. I will never buy this bowl again nor will I recommend it to anyone. If your kids have this mug I would check to make sure it doesn't happen to them.