PPSU Safety Material Deforming resistance, heat resistance up to 200°C,will not produce any toxic. High quality and durable. Transparent like glass, easy to clean Stable,can repeatly sterilize PPSU is an environment friendly plastics that is light weight but durable. Transparent like glass, stable and can withstand sterilize. Soft nipple can protect baby's lips - Breast-shaped nipple design promotes natural latch-on similar to the breast,making it easier for your baby to switch between breast and bottle feeding Quadruple Nipple Design - Reduce the symptopms of colic, gas and spit up. Anti-colic 3D Designed Ring - 3D Designed Ring increase durable, reduce toungue furred and keep toungue healthy. Good air flow to prevent baby sucking in too much air Bumps nipple design - Similar to breast, baby enjoy a more comfortable and contented feed. Cross shape hole - Easy for baby to drink Auto Straw - Baby can drink easily Enlarged one way backflow valve, allow air ventilation, will not happen leakage Prevent leakage when feeding, reduce air pressure and bubble when feeding to prevent baby from choking Arc-shape Design , Easy to hold. Comfortable handle, baby can hold it easily when drinking Comfortable Handle - Train baby to drink Wider Neck Bottle Design - 50mm Wider Neck PP Double Seal Cover - Safety and Steady. Bottle cap and nipple carefully designed to prevent leakage and anti-dust. Anti Dust & Anti Leakage PUKU Warming Tips Sterilizing bottles kills bacteria that may be harmful to your baby. Steam the bottle together with water. After sterilize do not put on the table to air dry or use tissue / dishcloth to dry it . Do not use your hand to handle the bottles. Use a pair of tongs to take the bottle the pot and put them on kitchen tissue to air dry.