Your pups already deliver plenty of fun to your home; with our dog driver costume, they can do it the FedEx way. This adorable dog outfit is perfect for costume parties, Halloween, and simply adding delight to any day. Small dog size: 15.74 - 19.68 chest. Medium dog size: 19.69 - 23.62 chest. Large dog size: 23.62 - 27.56 chest.