Food grade silicone is BPA free, non-toxic, harmless ,and super soft silicone won’t hurt baby’s gum.High temperature resistance 320℃ , high temperature resistant for sterilization.Silicone is a breathing material , Can keep the food fresh for a long time. 2:peristaltic nipples: One is that the baby uses a peristaltic or compression motion to actually push the milk out of the nipple and breast. So peristaltic nipples are made from soft food grade silicone and shaped to mimic the breast in form and function, suitable for baby to suck milk from the feeding bottles.