The size of the cage should be proportional to the size of the dog. The minimum recommended cage is XXL, but the best option would be a XL or even an XXL, so that your Shiba Inu has enough room to move and play.
The material of the cage is also important. Some sellers offer cages in metal or plastic materials, but both have some disadvantages: metal can rust and plastic needs to be replaced often because it is not durable.
Stainless steel cages are ideal, as they are resistant to rust and dogs usually do not chew on them.