Designed specifically for Stanley 40oz and 30oz tumblers, these blue whale-themed straw covers provide a secure seal for your cup's straw Made from food-grade silicone that's durable, flexible, and easy to clean, with 10mm diameter opening to fit standard straws Package contains 4 decorative blue whale straw covers that add a playful touch to your Stanley cup experience Acts as a protective cap stopper to prevent spills and keep debris out of your straw when not in use Simply slip the cover onto your straw - the snug fit ensures it stays in place while allowing easy removal when needed 1