I made this to have a meal for our kid with us all the time. The small flasks top outside fits in a MAM baby bottle ( http://www.mambaby.com/uk/the-products/info-bottles-cups/bottles/ ) so you don't have to be "careful" when you pour the formula in to the water in the bottle. Just turn the small flask upside down in the top of the MAM bottle. The little measuring cup that comes with SEMPERs formula feeding will also fit inside the top of the flask so you don't spill when you fill the flask with the formula. :) There are two flasks. One with a thredded top and one with just a push fit. Your choise. :)