1. You don’t get clumps under the air filters. Mixing a bottle with those things just doesn’t always go well if you’re approaching the max amount of formula in that size bottle. There’s not enough room for the water and formula to mix.
2. These DO NOT LEAK. Period. They just travel and shake well.
3. You don’t have to use the little white bottle discs. Or if you use them to prevent water from leaking, you can the. Use this to mix formula. Personally, I hate traveling all day with premade bottles. It’s a lot to carry in 10 oz bottles. It’s so much easier to pack one formula container, one water container and a couple of lids.