Closer to natural breastfeeding – Designed to be most like mom, The Naturalatch silicone nipple encourages proper latching, promotes healthy feeding and allows you to easily switch between breast and bottle. Anti-colic feeding – Soft, disposable liner contracts while baby feeds to mimic breastfeeding. This prevents air from mixing with Milk and allows air-free FEEDING, reducing colic, gas and fussiness. Pre-sterilized for cleanliness – Pre-Sterilized Liners guarantee your bottle is clean and minimize clean-up time. They are also recyclable. (Does not include nipple and ring) (can be recycled at most grocery and mass retail store recycling bins) Fast bottle warming – Drop-Ins Liners are thin for quick and easy warming. Designed for on the go moms – Nurser bottles are conveniently designed with Pre-Sterilized disposable Liners to make bottle time easy for home or on the go.