Hey Dr Brown's bottle users - if you're tired of losing those little plastic caps or need extras for daycare, this 10-pack is exactly what you need! These green caps fit perfectly on the narrow neck Dr Brown's bottles (the 8oz ones) and create a really secure, leak-proof seal thanks to the built-in silicone gasket. I've been using them for storing expressed milk in the fridge and for pre-measuring formula powder when we're out and about - so convenient! They're made from durable PP plastic that doesn't crack or warp, even after going through the dishwasher a bunch of times. The non-slip ridges make them easy to grip when your hands are wet or tired. We keep some at home, some in the diaper bag, and sent a few to daycare - having extras means you're never searching for that one missing cap when you need to pack bottles quickly. They work great with both the glass and plastic Dr Brown's bottles. At 1.85 inches in diameter, they're the exact same size as the originals. Seriously, if you use Dr Brown's system, these replacement caps are totally worth having on hand - they've made bottle prep and storage so much easier for this sleep-deprived parent!