You will note that of the two I have, they are identically sized, both in a size “small”, but one is labeled small 11 to 13 inch back guideline, the second 13 to 15 inch back length guideline. This will really show how often you would find that per the tag, you would buy a size in the Star Wars items, but in fact, would find that it ran small so to speak. The problem was that they were actually mislabeling their items. While back length is really not the only guideline to size this, certainly if your dog is of average girth, you would buy based on the length, however, if you have a dog, that is a specially stout, you would probably want to go up in size. Please ask if you have any questions as one of these is vaguely wider, and one is maybe 3/4 of an inch longer…
I also have baseball cap, harness, neckerchief, collars, TOYS, small pet carrier with the R2D2 motif- but many items from the discontinued Petco STARWARS Pet Fan Collectio, listed and yet to list- ASK :)