[Spill Stopper Accessories:Does your straw cup leak? Our leak proof kit is the best solution to your trouble it keeps your tumbler spill stop Scope of Application:This leak proof stopper is compatible with YETI straw mug: 16 oz / 20 oz / 24 oz / 25 oz / 26 oz / 39 oz Multi-protection:The straw cover topper cap and spill stopper doubly prevent water from spilling and keep contaminants from getting inside the mug Vent-hole Design:The round leak stopper must have vent-hole to equalize the air pressure making it easier to drink. Even if the mug is knocked over only a few drops will come out High Quality Silicone:The spill proof accessories is made of food grade silicone BPA free non-toxic. Soft silicone is easy to install and clean]