The Boob Glass Bottle is the most innovative baby bottle on the market today. The nipple design, CleanFlow Vent System, silicone sleeve, and bottle are state-of-the-art and use today's best design and materials. The silicone sleeve reduces slips and provides the Boob Glass Bottle with an excellent cushion against bumps and drops. Transitioning from breast-to-bottle, bottle-to-breast, or bottle-to-bottle can be frustrating and delicate, but the Boob Bottle's innovation and technology make it a "natural" choice for quick and easy transitions. Available in 5oz and 8oz sizes and various colors.JOOVY