The Celltei® Birdie GoGo is a very compact size for the very small birds such as Budgies, Canaries, Painted Conures, Pocket Parrots etc. It opens all the way and lays flat when not use.
Many customers, however, would opt to have a larger size so that they can put in a lot of toys to keep the bird busy. Some would put in furniture such as a sleeping tent for a overnight trip as well. It really depends on the planned activities to choose the right carrier size.
Because the Birdie GoGo is so compact and made of stainless steel mesh, it is also desirable for other small animals as well.