The Joovy Boob Baby Bottle is the most innovative baby bottle on the market today. The new nipple design, CleanFlow vent and bottle are state-of-the-art and use today's best design and materials. The PPSU Boob Baby Bottle stands up to repeated sterilization, will not absorb odor or color, and is BPA, phthalate and lead free. It's ergonomically designed to fit nicely in your hand. The grey color emphasizes a "clean" look and milk appears whiter vs. amber-colored bottles. Each bottle is individually shrink-wrapped to ensure the highest level of cleanliness. Our 1-piece CleanFlow vent is easy to clean. There is no assembly needed and no need to touch any part that comes in contact with the milk or formula. It provides consistent venting regardless of how the bottle is held. The vent's tabs fit perfectly into the bottle's neck to eliminate any miss-fittings that can cause leaks and inconsistent liquid flow. The nipples have been designed to make transitioning from breastfeeding to bottle-feeding and bottle-feeding to breastfeeding an easy and natural process. The large diameter base and nipple length assist your baby in properly "latching" onto the nipple. Available in 5 flow rates, our nipples are molded (not cut) with the appropriate size hole and are tested for consistency throughout production. We also take the extra step of baking our nipples. Baking strengthens the silicone to help prevent nipple collapse while providing constant softness. The innovative insulator is designed to keep liquids near their desired feeding temperatures longer. It also extends the thawing time when traveling with frozen breast milk. The clear insulator allows you see how much liquid is in the bottle. It works with the nipple/collar installed, as well as breast pump adapter and bottle cap.