I see many people asking about which cages are good, so here’s a list of some good cages. With the critter nation cages(or any cage), make sure to get the ones with 1/2 inch or LESS bar spacing or your gliders will be able to escape. Ferret nation looks similar but the bar spacing is too large.
EBAY(All basically the same cage, minor differences. I’d go for one with shelves and ladders, and remove all ladders and all but one shelf. If you get one with wooden perches, Id suggest removing them as they may be made of unsafe wood. I’d suggest zip tying the small doors as well.):
EXOTIC NUTRITION(I would buy only cages here, not anything else. Their food and wheels are not good in many owner's opinions.):
DCN/ALT(shop around for good prices, but stay away from the similar looking ‘prevue hendryx’ cages. They have much smaller doors which make them hard to clean.):