Each is a full-size pet carrier, but once you're done with it, you're done with the bulkiness too, because it quickly folds down to just 3" to 4- " thick (depending on model)! Pops open just as easily! No loose parts to lose. Approved for use on airlines worldwide, and allows your pet maximum visibility and ventilation during the trip. Great for trips to the vet too! Two smallest models have top-loading doors; great for cats. Structural ABS plastic. "Open" dimensions given; width x length x height. Makes Travel Easier On Your Pet!