We travel quite a bit and thought these would be a great idea for our child. Well that little problem solver figured out how to take the lid off in a matter of minutes. Needless to say he enjoyed flinging his snack EVERYWHERE!! We continued to use these until we could order a new set with screw on lids. (Munchkin makes those too!!!) Thankfully mynlittle one has yet to figure out the lids on those ones.