The Thinkbaby Starter Set is the perfect gift set for any new parent.The set includes two polypropylene 5 oz baby bottles. The bottles are outfitted with cross cut slow flow nipples (designed for 0 to 3 months), two polypropylene 9 oz baby bottles with medium flow nipples (designed for 3 to 6 months), and finally, two fast flow nipples are included (designed for 6 to 12 months).All of the nipples feature anti-colic design. Anti-colic systems help reduce the incidence of gas and spit up by reducing the vacuum pressure created while the child is drinking. All of the bottle parts can be washed in the dishwasher, (recommend utilizing the top rack). With the starter set, you get every speed of nipple (all nipples are labeled Level 1, 2 and 3 for easy identification). This will provide you with the ability to see which flow rate works best for your little one, as all children feed at different rates. This also means that if you purchase this for a gift, you won't have to concern yourself with making sure that you've purchased the appropriate product. Best of all though is that this set is priced better than most two packs of bottles. Plus you get a total of six nipples. All thinkbaby products are free of Bisphenol-A, nitrosamines, phthalates, melamine, Tritan, lead, PVC, and biologically harmful chemicals. All products are recommended by Healthy Child Healthy World.