M.K.
The entire line of Playtex cups! My First Sipster (stage1), Sipster (stage 2), Insulator (3) and Coolster Tumbler (4). I've been using these for 3 years now and they *never* leak when dropped, thrown, tipped over...or even left laying sideways on the carpet. The only way anything has come out is when the kids were toddlers and would vigorously pound them, upside down on the high chair tray. And even then, maybe a drop or two would come out. I put these in the dishwasher and even that doesn't negatively impact them or shorten their life.