What Is the Difference Between Avent Bottles? by Nursing Angel published on 2021-10-22T05:04:37Z Polypropylene (pp) – classic bottles polypropylene appears to look milky or slightly cloudy. Using BPA-free plastic, containers made from polypropylene are also slightly flexible. Bottles made from polypropylene are milky in colour, have a softer plastic and use an adapter ring. They are known as “classic” bottles and are typically sold in a blue/white box. Visit Us:- https://www.nursingangel.com.au/blogs/news/avent-bottles-what-is-the-difference-between-pes-advanced-pp-natural-bottles-and-philips-aven