The system includes two files a 5X1 array and a 5X2 array, both of which can be assembled using 1/4" dowel rod stock. I recommend using wooden dowels since they compress nicely along the grain.

Dropper bottles overlap, but still allow for visibility of the color labels. Using Vallejo bottles, the max height with the bottles in position is only 42mm, which I designed to specifically fit into the rear compartments of this Mount-It! Drawer (Fits 30 dropper bottles in the largest compartment) that I just installed on my painting desk: