With only two parts, the Born Free Breeze Glass Bottle is the easiest to clean bottle system that both you and your baby will love. The anti-colic design with ActiveFlow Vent puts baby in flow-control, and the ������Just like Mom������ nipple makes it easy to alternate between breast and bottle feeding. Born Free Breeze BPA-free Glass Bottles are made from ThermaSafe glass and can safely go from the freezer to boiling water. Only 2-Pieces Anti-Colic Design 'Just Like Mom' Nipple Easiest to Clean Level 1 Slow Flow Nipple (0M+) Every baby is different, and there's no rush, so please use these guidelines along with your intuition for when to switch to the next level. Level 1 Slow Flow Nipples are included with 5 ounces. Breeze Bottles and can be purchased separately. Level 2 Medium Flow Nipple (1M+) Every baby is different, and there's no rush, so please use these guidelines along with your intuition for when to switch to the next level. Level 2 Medium Flow Nipples are included with 9 ounces. Breeze Bottles and can be purchased separately. Level 3 Fast Flow Nipple (3M+) Every baby is different, and there's no rush, so please use these guidelines along with your intuition for when to switch to the next level. Level 3 Fast Flow Nipples are included with gift sets and can be purchased separately. Y-Cut Thicker Fluids Nipple (6M+) Every baby is different, and there's no rush, so please use these guidelines along with your intuition for when to switch to the next level. Y-Cut Thicker Fluid Replacement Nipples can be purchased separately.