This item is used in maternity hospitals. I have used it for about a month. Pigeon Breastfeeding Realism Direct-Attach Baby Bottle 200ml + Nipple (Low Burden, High Flow) + Lid 2 Sets [For General Newborns] This is made of heat-resistant glass, which is strong and easy to clean, and can be sterilized by boiling or chemical solution. The nipple allows the baby to feed with a sensation close to breastfeeding, developed from research on mammals. Regardless of the sterilization time or number of uses, replace the nipple if any abnormalities such as tearing, cutting, or deterioration are observed.