The containers do separate. Out of the box they have a piece of thin cardboard between them which I removed. Each container has 4 plastic pegs on the bottom which fit into sockets on the top so you can switch them with other containers and they stay together while they are in motion. I have asked MTH to come out with extra containers, like they did with the premier double-stacks, and was told that was going to be done. When is a good guess.