Bests & Worsts Reviews from Amazon

These bottles are terrific! We love the safety from chemicals and piece of mind of the glass as opposed to plastic. Another benefit is that breast milk and formula can be warmed much more quickly through the glass bottles than through plastic. The nipples also work great, and we love that AVENT has a preemie (a.ka. "First Flow, Number 0") size also available, which is an even slower nipple than the "Newborn, Number 1" size that ships standard with these bottles. The nipple size descriptions can be confusing, so I hope that the size description below is helpful to others. AVENT nipple sizes ordered from Slowest to Fastest: - "First Flow, Number 0" (think of it as preemie size, must be ordered separately from bottles) - "Newborn, Number 1, 0m+" -- comes with the 4 Ounce AVENT Natural Glass Bottles - "Slow Flow, Number 2, 1m+" -- comes with the 8 Ounce AVENT Natural Glass Bottles - "Medium Flow, Number 3, 3m+" - "Fast Flow, Number 4, 6m+" Part of the confusion arises because most of the nipple size charts don't even show that the "First Flow" nipple size exists. However, there is an excellent chart on Amazon's product description for the "First Flow" nipples that shows all the sizes. I have pasted the picture of this chart to this review for ease of reference.