The Boomer Ball is designed for those larger-than-life characters who love to chase and conquer - typically Bull Terriers and other macho breeds. It is designed not to be picked up by the dog, so should be a size bigger than the dog can carry. It can also be a therapeutic toy to enrich the environment of elephants, pigs, polar bears or any other bored, inquisitive animal. Sizes4 = 110mm6 = 150mm8 = 200mm10 = 250mm