These were used at a maternity clinic. They were used for about a month. Pigeon Breastfeeding Realism Direct-Feed Baby Bottle 100ml (for general newborns) Yellow, set of 2 Made of heat-resistant glass, which is strong and easy to clean, allowing for boiling and chemical sterilization. Uses a nipple developed from research on breastfeeding animals, allowing the baby to feed with a sensation similar to breastfeeding. Replace the nipple if any abnormalities such as tearing, cutting, or deterioration are observed, regardless of sterilization time or number of uses.