A finished model stays in good condition exactly as long as dust stays off it. Display cases are the transparent covers and boxes that shut it away while leaving it visible. The range covers acrylic covers in a spread of sizes, cases with a wooden or mirrored base, and turntable versions that let you walk round a model without touching it.
Two decisions matter: the internal dimensions, which people habitually get wrong by a centimetre, and the base, which changes how the model reads on a shelf. Both are covered below, along with how to clean acrylic without ruining it.
Dust on a model cannot simply be wiped off. It settles between rigging, into undercarriage bays and onto matt varnished surfaces, where wiping leaves shiny smears behind. A case prevents all of that, because you place the model once and never touch it again. The second reason is mechanical: aerials, exhausts and propellers are at their most vulnerable precisely when a visitor wants to pick the model up for a closer look.
Measure the model in all three axes and add at least ten millimetres on every side. On aircraft, remember the span and the tailplane; on ships the bowsprit and the masts; on armour a barrel traversed to one side. A model that only just fits will not come out again without a scratch.
A cover on a wooden base reads as a finished installation and can be picked up as one piece. Versions with a mirrored base show the underside as well, which is worth having for aircraft with detailed wheel bays. Turntable cases earn their keep at competitions and in photography, because you can go round the subject without moving it.
Most modelling cases are acrylic. It is light, it does not shatter and it drills cleanly if you want to run a cable through the base for lighting. Acrylic scratches easily, though, so clean it with a microfibre cloth and water, never with the thinners and cleaners intended for paint — those will haze or attack the surface.
Buy for the largest model you intend to put inside, not the one on the bench today. Tall subjects such as aircraft models on a stand are the usual reason people end up buying twice. The rest of the workspace is in modelling workbench equipment.