Allows Baby To Use The Breastfeeding Movement They'Ve Learned Through The Breast. Made Of 100% Silicone, Extremely Soft And Pliable To Allow For Natural And Smooth Movement Of The Tongue. Ventilation System (Avs™) Reduces Air Entry, Which Is A Potential Cause Of Colic. Easy Grip Shape Helps Hold The Bottle.The Bottles Are Specially Designed With Anti-Twist Caps.The Bottle Is Made Of Polypropylene (Pp), A Strong And Lightweight Material.Bpa Free.