I bought this system for my son because I was looking for a very low flow nipple to help prevent his gas. The primary problem with this system is the vent: 1) As a sleep-deprived parent, the simpler the better. I in a sleep-deprived haze have forgotten to put the vent in when assembling the bottle and have gotten formula everywhere as a result; 2) the vent and the bottom piece assembly must be very dry when assembled (so you have to dry everything with a paper towel before assembling because even a dishwasher with a dry cycle doesn't make them dry) or they leak--and you get formula everywhere; 3) you can't buy replacement vents anyhwhere except from Playtex. This is a problem since the vents will fall out of many dishwasher baskets and 4) You can't use an electric bottle warmer to heat the bottles. All in all, the Dr. Brown's system is better. This system isn't worth the expense.