Boon Snug Reusable Stretchy Silicone Spout Cup & Lids are unique no spill sippy cups for weaning your precious little one off the bottle. Boon Snug Reusable Stretchy Silicone Spout Cup Lids fit over any regular cup with a 2.5"-3.75" diameter and instantly prevent that cup from spewing its contents when knocked over or tossed off a high chair (not that that's ever happened). The lids are gentle on teeth and a great way to transition your baby over to regular sippy cups. Boon sippy lids are popular with daycare providers, crunchy moms and the ideal solution for a growing number of parents going plastic free. When the silicone lid is stretched over a cup, the suction keeps the lid in place making your new sippy cup spill resistant. The flexible silicone spout is soft and gentle on teeth and gums. So rather you are out at a restaurant or enjoying a day at the beach - don't forget your Boon Silicone lid. It will meet your needs, no matter where your day takes you.