Keep using your Natural-Feel Baby Bottles™ as baby grows! These extra silicone nipples are available in a range of styles and stages to keep up with maturing babies. Pack of 2. Comotomo™ Natural-Feel bottles sold separately. Slow Flow features one hole (for newborns-3 mos.), Medium Flow features two holes (for 3 mos.-6 mos.), Fast Flow features 3 holes (for 6 mos. and up), and Variable Flow features a Y cut (for 6 mos. and up) Ideal for breastfed babies who take an occasional bottle or for transitioning nursing babies to bottles Unlike plastic, silicone is a natural material that has no open pores to harbor bacteria. Scratch resistant, hypoallergenic and BPA-free. Top-rack dishwasher and microwave safe. May be boiled.