Pura's feeding systems are not only safe, but the new Natural Vent Nipple™ was designed to mimic the variable flow rate of breast feeding. These new nipples employ a new shape that promotes a better seal between the baby and the nipple, an elongated vent to reduce colic and spit-ups, and the use of multiple holes in the tip to achieve different flow rates. In addition, we have added a Y-cut version for thicker liquids and/or even faster flow.