The unique Mixie Baby Bottle conveniently allows you to prepare baby's bottle ahead of time. The patented compartment of the Mixie Baby Bottle features an airtight design so you won't worry about any messy surprises. Using the Mixie Baby Bottle is easy: Put formula in the compartment and place water in the bottle. When you're ready to feed baby, simply push the button on the bottom of the Mixie Baby Bottle to release the formula into the water and shake the bottle to mix well-Unique Mixie Baby Bottle. -Conveniently allows you to prepare baby's bottle ahead of time. -Makes bottle feeding easy. -To use: Place formula in compartment and water in bottle, then push the button and shake well to mix. -Patented, airtight compartment. -Compartment lid is free-floating agitator that mixes formula and prevents clumps. -Vented nipples minimize colic. -Dishwasher- and microwave-safe. -BPA, phthalate- and PVC-free. -100% silicone nipple. -Polypropylene bottle. Sizing:-4-oz. Mixie Baby Bottle: Capacity of 2 formula scoops and includes a Stage 1 nipple. -8-oz. Mixie Baby Bottle: Capacity of 4 formula scoops and includes Stage 2 nipple.