Dual Anti-Colic Vent, Air goes in, milk comes out to ensure ideal air circulation to reduce unwanted colic, spit up, burping and gas. Comotomo baby bottles are designed to most closely mimic breastfeeding to reduce bottle rejection and nipple confusion issues. Ultra wide-neck design allows easy cleaning by hand without a brush; Safe in microwave, boiling water, dishwashers and sterilizers. Nipple and body is made of 100% safe hygienic medical grade silicone. Safe: No BPA, PVC, Phthalates, Nitrosamine.