... the same pressure both inside and outside of the bottle, bottle feeding completely solved trouble of the flatulence; reduce hiccups, spits, ... month/ 3~6 month/ Above 6 monthCertificationSGS,FDA,GTQSafty:free of BPA, phthalates, & PVC, non-toxic, lead-freeTemperature:High/ ... to open the mouth and feel asbreastfeeding(5) The nipple make of 100% liquid silicone nipple rubber , more sofe and clearAdvantage ...