I am a big fan of the Playtex liner system. It’s easy and clean. The drops ins are great because you don’t have to worry about it slipping out the end of the bottle like you do the older style. That all being said, I find that I’m not a huge fan of the expandable feature of these liners because they don’t give you an accurate reading of the liquid you are putting in your formula. This can make your baby very sick. To remedy this, we use a measuring cup to measure out the liquid before adding it to the liner. So say we are measuring out 8oz of liquid, sometimes the liner expands properly and it says 8oz, sometimes it looks like 9oz and other times it looks like 7oz. It’s definitely a flaw in the product’s design. We’re going to keep using them because we don’t mind measuring first, but I hope they fix the problem.