You can print 1 of each base to have a long shelf or print 2 of both to have an extra large shelf! One base is 7x4.75 inches so you could just print one if you want a small display shelf. The honeycomb design reduces how much material is used while maintaining structural integrity so you won't have to worry about it collapsing on you (PLA or PETG recommended for strength). I also recommend using a 20% infill so the structure is strong, although you could go down to 10% if you really want to save some filament. If you are planning to put something heavier on the shelf you can also print some legs to use in the middle of the shelf.

Update (09/2/24): Added V2 for the base plate models, this design has larger connectors that give the shelf more rigidity if using a larger shelf with more than one base piece.