Although I breastfed the majority of the time, we invested in this container for the few times we needed formula while out and about. It came in handy because I could have formula premeasured and could make a bottle whenever needed instead of worrying that it would go back before we could use it.
As a bonus, this container can be used again and again as they get older. We now use it as a snack container. We keep a different snacks in each slot so that we always have a variety of snacks on hand. I've had many people ask me where I found my snack container and they are surprised to learn it is actually a formula container. As a parent, we all need little shortcut ideas and this has been wonderful because I know there is always a snack ready and waiting in his diaper bag.