Brand new MAM Easy Start Anti-Colic Bottles. 1 still in the plastic bag. But they are both brand new. The nipple size is 0. 4.5 ounce The patented vented base of the MAM Easy Start Anti-Colic Bottle ensures that babies can drink calmly and relax. The ventilation holes in the base regulate pressure balance and airflow, and as the bottle ventilates via the bottom, milk flows undisturbed without air bubbles, feeding without interruption. Medical studies suggest that the enhanced vented base reduces colic symptoms in 80% of babies who use it. The result means no more air swallowing, more relaxed drinking, and more quiet nights!!!!