NUK First Choice+Flow Control Teat: helps the transition to independent drinkingThe special NUK First Choice+Flow Control teat lets babies control the flow themselves when they  are  drinking.  No  matter  if  they  want  to  drink  quickly  or  slowly  or  if  whatever  you  are feeding is thin or thick.Just as the baby likes it. In  addition,  the  teat  is  also  leak-proof.  This  is  because  the  innovative  Y-opening  of  the  teat only opens when your baby is sucking and widens depending on the sucking strength of your baby. Together with the NUK Anti-Colic Air System, this ensures a controlled drinking flow.