Cubes are composed of panels that are about 14”x14” that you can snap together using circular multi-connectors; usually people connect the panels to form cubbies used as storage. The panels are made of a wire grid, and there are different options for how many holes there are (and therefore, how closely spaced the wires are). The option you want is the 9x9 grid, which has closely-spaced wires. There are also 8x8 grids, which can end up strangling the pet, and 5x5 grids, which are way too big for any rodent-sized pets.