Our Soft and anti collapse ribbed teat is designed for growing babies. The comfort petals and natural teat shape allows natural latch on makes it easy to combined breast and bottle feeding. Philips Avent Natural variable flow nipple has a slot shaped opening that can change the flow of milk. Simply turn the bottle to line up the i, ii, or iii marking on the nipple with your baby's nose to choose between slow, medium, and fast flow. The wide, breast shaped nipples promote natural latch on so you can easily combine breastfeeding and bottle feeding., and the unique comfort petals inside the nipple increase softness and flexibility without nipple collapse. The nipples are made of flavorless, odourless silicone that resists discolouring and stickiness.