These are fabulous!! so easy to open, just press down on the top button to open, and then press down again to lock.  Genius design, especially for us ladies with arthritis. Even if you have no problems unscrewing wide lids, how much easier and faster to just press the lid's button and have access to the container's contents. I am LOVING these!! The lids unassembled for washing.. I would definitely get these again in all sizes.