PRESS-TO-CLOSE, TWIST-TO-OPEN (PCTO )- Hassle-free handling with no spillage; one handed closure (Patent Pending). PRECAUTIONARY DESIGN: If the liquid in the bottle is too hot (above 70 deg Celsius), air pressure will force the fluid out from the sides. This works as a precautionary in case the milk is too hot for consumption. REMINDER: 2OZ BOTTLE COMES WITH EXTRA SLOW FLOW NIPPLES | MULTI-FUNCTIONAL FEEDING SYSTEM- when the baby no longer needs the bottle, the bottle can be transformed into a food container, water bottle, storage container with our optional accessories. Let our bottle grow with your child. | LIKE A MOTHER'S BREAST / MORE NUTRIENTS, LESS AIR- Air venting bypasses the milk, minimizing air bubbles & oxidation of nutrients. Built-in anti-colic air vent reduces air intake. Elliptical-shaped silicone teat simulate a latching experience. Off-center teat enables your baby to feed in natural upright position. | STACKABLE & EASY TO CLEAN- “soft-square” design prevents the bottle from rolling away and allows it to be stackable to optimize storage | BPA, BPS, PVC, & PHTHALATES FREE- created with NSF certifieSU that combines advantages of both glass and plastic material; lightweight d PP& odor free; Shatter resistant and Dishwasher safe (top rack only)