NUK First Choice Smooth Flow Anti-Colic Bottles are the anti-colic solution for bottle feeding with no gas, bubbles or tears. From the #1 hospital trusted brand for feeding, the NUK First Choice Smooth Flow Anti-Colic Bottle has an anti-colic air vent in the nipple that prevents baby from swallowing air when drinking. 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. Bottle colors may vary. Colors may vary.