Instruct: Classify an Amazon review as either positive or negative.
Query: These bottles leak!

Used the old design when our 3yo was a baby and they were great. But the new design leaks, leaks, leaks! Called Playtex - they said to assemble the bottles dry and they sent me some new o-rings. I tried again but they still would leak significantly from time to time. The seal can be broken by the baby sucking or if you drip some formula down the side of the bottle when you're filling it. There's nothing like having to heat up a fresh bottle in the middle of the night because the first one leaked all over the table when you stopped to burp the baby. Buy something else until Playtex fixes the design.