Comotomo Baby Bottles feature innovative and sensible design to closely mimic breastfeeding. The breast-like wide mound design and the soft, skin-like silicone material makes it ideal for babies to transition from breast to bottle, and back! Unlike any other bottles in the market, Comotomo Baby Bottles feature a truly wide-neck design (3 inches in diameter) to make cleaning them completely hassle free. The silicone material used is high quality food contact grade that is not only 100% non-toxic, but also safe in microwave, boiling water, dishwashers and sterilizers. Comotomo Baby Bottles were thoughtfully designed with convenience and function in mind. The nipples feature built in dual anti-colic vents (without any extra parts) to allow consistent milk flow without unwanted air-intake to reduce colic. *5oz Bottles comes with the Slow Flow Nipples (0-3months) and the 8oz Bottles comes with the Medium Flow Nipples (3-6months). Faster flows available separately.