Pigeon Flexible Slim Neck Nipple Size S x3Backed by over 60 years of research on babys natural suckling motion, our Flexible Slim Neck Nipple is so soft it flexes to the movements of babies mouth and bends naturally to babys mouth movement. The nursing bottles Air Ventilation System (AVS) reduces intake of gas, a potential cause of colic. For 0+ months. The opening of the nipple is round cut which allows milk to flow out consistently and gradually. Newborns have yet to develop any jaw