Smooth Flow nipple allows baby to control flow rate SafeTemp indicator shows when milk is too hot Nipple mimics the shape of mom's nursing nipple during breastfeeding Wide neck bottle is easy to clean BPA free, dishwasher safe (top rack) NUK Smooth Flow Bottles are the anti-colic solution for bottle feeding, featuring a unique nipple design that allows baby to control the flow rate for colic-free feeding. This Smooth Flow nipple adjusts the flow based on how your baby drinks, adapting to their suction strength to ensure they will always have the right flow rate. The SafeTemp temperature indicator lets you know when milk is too hot with just a glance. The blue thermometer indicator fades when milk is too hot and reappears when milk has cooled and is safe to drink. Colors may vary.