Nipple flow levels, explained

Every nipple we make carries a code moulded into the silicone: SS, S, M, L or LL. Those are our five flow levels, 0 to 4, and they are the only sizing system on this site. One wide-neck fit means any level screws onto any bottle we sell.

The ladder

• Level 0 (SS), extra slow. A dribble. We mark it for newborns from day one; it also ships on our 3 oz bottles.
• Level 1 (S), slow. From about 1 month. The 5 oz bottles carry this one out of the box.
• Level 2 (M), medium. From about 3 months. Standard on the 8 oz glass and the 9 oz PPSU.
• Level 3 (L), large. From about 6 months, for babies emptying a medium too slowly for their patience.
• Level 4 (LL), fast. From about 9 months, for a drinker with opinions about waiting.

Reading the feed, not the label

The ages are markings, not deadlines. Babies tell you when a flow is wrong: sputtering and milk escaping at the corners usually mean too fast; long feeds where the baby works hard, gets cross and tires before finishing usually mean too slow. When the bottle is fine and only the pace is off, swap the nipple, not the bottle. Each 3-pack costs less than any bottle we make.

About the vents

Every level has the same vent design at the base. The vents let air back into the bottle as your baby drinks, so the nipple keeps its shape instead of collapsing flat and interrupting the feed. Check them when you wash: a blocked vent makes a slow nipple slower.

Not sure where your baby lands? The flow finder asks two questions and names a level.