The bottle's unique design is easy to hold. A medical grade type of plastic is used, which has been specially formulated to be free of PVC, BPA, nitrosamines and phthalates. Each twin pack of thinkbaby 9oz baby bottles comes with: ~ bottle base ~ collar ring ~ travel cap ~ stage 1 - cross cut - slow flow - anti-colic nipple Patented venting system reduces incidence of gas and spit-up. Venting systems have also been shown to reduce the risk of middle-ear infections. The venting system allows air to flow back into the bottle reducing the vacuum created while your child is nursing. Simple one piece design system so no more worry about losing and cleaning pieces. Extra soft nipples made from high grade silicone provide easier transition from breastfeeding to bottle feeding. Dishwasher safe. Top rack recommended.