The old Bush Herp ones or the failed Neodesha Plastics company design? There were slight differences between the 2 designs regarding the vents.
Slant front or standard? Glass or plexi fronts?

I used these for years. The slant fronts with sliding glass doors with the steel rack to stack them on and they were great. 100% escape proof. Nothing was going to get out of them.

They take up a lot of room since you cannot stack them without the rack but they make great display type cages. Hold heat and humidity very well.

I really like them. It's a shame you can only get used ones now.

Here's a stack of 3 foot slant fronts.