Not all costumes are available in all sizes. Please refer to the individual product page for actual available sizes.
For Pet Costumes: measuring should be done along the dog's backbone from the base of the head to the base of the tail. However, it's important that the dog's girth (chest) be taken into account as well as the back length measurement. If the dog has a large girth, going up a size is always a smart choice, since some additional fabric will be used up.