Added convenience of 2 extra packs of Silicone Nipples included with this set (2 nipples in each set). The bottles come with Fast Flow nipples for 6+ months, 3 holes; extra sets include another pack of Medium, and 1pack of Variable Flow for 6+ months. Comotomo’s innovative approach has changed the status quo of baby bottles into the next best thing to mommy. Natural shaped silicone nipples replicate the breast-feeding experience and minimize nipple confusion. Babies love the skin-like material for the bottle; it’s squeezable and soft. Safety is on everyone’s mind, and Comotomo’s products are at the top of the list in all categories of concern: 100% free of BPA, PVC, Phthalate and Nitrosamine. Scratch resistant medical grade silicone will not harbor bacteria like scratch prone plastics do. Wide-neck design makes cleaning easy, and high temperature compatibility make it possible to boil the bottles and nipples for ultimate cleaning or sterilization. Anti-colic venting ensures baby has a happy tummy by eliminating vacuum build up. All this, and a truly non-leaking bottle.