Prevue Pet Products 58500 Ferret Stack | Add-On Set — EXPAND your Ferret Stack home by a full floor level when your pet needs more space! This full-story add-on expands your 1-, 2-, or 3-Story cage up one floor, for more room to play, live, and explore. The Add-On Set includes one plastic platform, two plastic ramps, and hardware for assembly and attachment to an existing Ferret Stack model cage. The large half-cage front door measures 15"W x 19.25"H, and features an "escape-proof" door lock. The Add-On Set cannot be used as a stand-alone cage. Cage portion measures 31"L x 20"W x 20"H. Wire spacing is 7/8-inch.