I bought displays for all of the current Star Wars helmets - singles for Luke's helmet and Leia's/Bouush helmet, a double for the Captain Rex and Commander Cody helmets, a triple for the Mando, Boba and Dark Trooper helmets and a quad for Vader, Stormtrooper, TIE Pilot and Biker Scout helmets.
These cases are the best for displaying the helmets (or other kits in their respective case).
At first, I didn't realise that each side had specific top/bottom as I just peeled off the protective backings and assembled as required and found that the sides didn't allow the top and bottom to sit properly.
It wasn't until I noticed that the "bottoms" of each side were slightly deeper than the "tops".
A quick reassembly, and I had everything sitting flush.
I also like the magnetic points in each base to ensure that each 3mm thick base remains intact.
Now i've got to get display cases for the rest of my Star Wars UCS, diorama and other collections.