Baby bottle

Large sized bottles typically holds 270 mL; the small size 150 mL. It is composed of a bottle itself, a nipple, a ring to seal the nipple to the bottle, a cap to cover the nipple and optionally a disposable liner. The height to width ratio of bottles is high (relative to adult cups) because it is needed to ensure the contents flood the nipple when used at normal angles; otherwise the baby will drink air.

"Vented" bottles allow air to enter the bottle while the baby is drinking without the need to break the baby's suction during feeding. Alternatively a bottle liner can be used to enclose the formula instead of directly in the bottle. The liner collapses as the formula is drained.

Bottles should be sterilized for babies under six months. Bottles can be sterilized by boiling in hot water, in a specialized bottle sterilization appliance (which typically uses steam) or in a specialized sterlization container that is microwaved. Modern bottles are difficult to sterilize in boiling water because they tend to float. Bottles were originally composed of glass which was dangerous when babies learned to feed themselves and hold the bottle. Modern bottles are unbreakable plastic.

The nipple itself is typically slimmer and more flexible than the mother's real nipple. Babies usually find feeding from the bottle easier than breastfeeding. Specialized nipples that mimic the shape of the breast exist to allow babies to switch back and forth between bottle feeding and breast feeding for cases where "nipple confusion" occurs. Nipples come in a selection of flow rates. Different flow rate nipples either have more holes or larger holes. The correct flow rate needs to selected based on the age of the infant.

Accessories for bottles include cleaning brushes and drying racks. Brushes may be specially designed for a specific manufacturer's bottles and nipples. The ring and nipple may be replaced by a storage lid. Bottle warmers warm previously made and refrigerated formula. Bottles may be designed to attach directly to a breast pump for a complete "feeding system" that maximizes the reuse of the components. Such systems include a variety of drinking spouts for when the child is older.