FARLIN SILICONE NIPPLE ANTI COLIC STEP 1, These silicone nipples are specially designed to ensure that the baby is familiar and comfortable with the mother's nipple shape. They ensure correct placement in baby's mouth and encourage healthy oral exercise,Lengthened air valve on base allows for constant flow of liquid and less ingestion of air, so prevents colic,Air valve allows constant flow of milk and less ingestion of air balances the liquid and air in the bottle,Stretchy base and durable circle