[Anastasia916]

What sandy said, but I don't fill the domes completely, there is still a tiny bit of space, it's not possible for me to fill the domes completely, I pump until my nipples are about to go into the suction hole, if I get to that within a minute or so of pumping, I move on to the next size. You might want to go ahead and order the next size domes just to have them handy for when you want to move on. If you aren't using an airlock I would suggest getting one also.