The design of the Critter Nation takes from the Ferret Nation many of the design features like the full open and removable doors, critter-proof door latches, large adjustable shelves with toy/bedding anchor points, wire ramps, and easy-to-clean and remove plastic pans. That's not all... MidWest also designed the Critter Nation so that NO tools are required to assemble the cage. No Tools! The design uses interlocking panels to securely lock the cage panels without the use of any screws, nuts, or bolts!