Each Sphere tower is closed at the top with a Sphere end tube. The end tube simulates shading for the levels below and protects the sphere mechanics from being coated. The size of the end tube must match the last Sphere plate. 

Sphere plates of one size can be stacked directly on top of one another without spacers. Therefore, the most economical arrangement is such that only plates of one size are stacked within a tree (of course, Sphere plates can be equipped with different sleeves if necessary). 

If different Sphere plates are to be stacked on top of each other within a tree, adapter disks must be placed between the different plates. In addition, the larger plates must be stacked under the smaller plates. Adapter disks only fit one size at the bottom, but all smaller sizes at the top.