No way to small

As said above, A dwarf hamster would need at least 450 square inches of unbroken/continuous floorspace in its habitat both so that it can have room for basic necessities (an exercise wheel between 6.5 and 8 inches in diameter, a couple hide-huts, a variety of wooden chews, a dish/bath of non-dusty sand to keep its fur clean with, etc). This cage does not provide that. It also does not provide a deep enough base for the up to 6" deep bedding a dwarf would need to be able to engage in natural burrowing behaviors. A cheaper and safer alternative to this cage would be a large plastic storage bin (at least 450 square inches of interior floorspace and 12"+ of height), as not only would it provide an all-around better environment for your pet: it would also be far safer and harder to escape. The Alaska cage is a good one for any breed of hamster and meets the minimum sizing of 80cm by 50cm.

This cage would not make a suitable enclosure for any hamster species. A Roborovski would need at least 450 square inches of unbroken/continuous floorspace in its territory, and bedding that is at least 4" deep (preferably 6") to allow for natural burrowing behaviors. This cage provides barely 100 square inches of interior floorspace, with the upper levels not counting towards that number from the perspective of a hamster. To save you some trouble, Petco does not currently sell a hamster cage that meets these requirements: you would do better looking in to getting a 40 Gallon Breeder Tank / 40 Gallon Terrarium (also sold at Petco, sometimes for under $100) or a large plastic storage bin/box.

This cage would not be an appropriate size for mice, with barely 100 square inches of interior floorspace in the base, and it would be easily escape-able because it is made of cheap materials that a mouse would be able to chew through. You would do better housing your mice in a 20 Gallon Long tank: as Petco does not currently sell a rodent cage that would be appropriate for mice, hamsters, or gerbils. Hope this helps!

A dwarf hamster would need at least 450 square inches of unbroken/continuous floorspace in its habitat both so that it can have room for basic necessities (an exercise wheel between 6.5 and 8 inches in diameter, a couple hide-huts, a variety of wooden chews, a dish/bath of non-dusty sand to keep its fur clean with, etc). This cage does not provide that. It also does not provide a deep enough base for the up to 6" deep bedding a dwarf would need to be able to engage in natural burrowing behaviors. A cheaper and safer alternative to this cage would be a large plastic storage bin (at least 450 square inches of interior floorspace and 12"+ of height), as not only would it provide an all-around better environment for your pet: it would also be far safer and harder to escape.

(Very important to note: gerbils, unlike hamsters, are social animals and must be kept in pairs or groups.) This cage would not provide a suitable environment for any amount of gerbils, and as they are rampant plastic-chewers: so it would be easily escape-able. Gerbils actually do better with closer to a foot of bedding, as they spend the majority of their time underground. I would opt for a 55 or 75 Gallon tank instead of a 40 gallon.

Hi Gerbil newbie, This cage is too small for gerbils. Thanks

Given the product dimensions, the interior base of the cage has no more than 100 square inches. The added levels would not count towards this measurement from the perspective of a hamster. Hope that helps! (I assume the Petco Customer Service reply made a typo / mistook your question for referring to cubic inches..)