The Philips Avent 4-ounce Natural bottles are the most natural way to bottle feed. The wide, breast-shaped nipples promote natural latch-on so you can easily combine breastfeeding and bottle feeding. The unique comfort petals inside the nipple increase softness and flexibility without nipple collapse, and the innovative twin valve anti-colic newborn-flow nipple helps newborns feed comfortably and easily. The ergonomic shape makes it comfortable for parents to hold and easy for small fingers to grasp. Assembly is simple with only a few parts and the wide bottle neck makes filling and cleaning easy. These Natural Philips Avent bottles are made from polypropylene, a BPA and BPS Free material, and work with all nipples and caps from the Natural line.