Most people know a Rat Terrier when they see one, but not everyone realizes that the breed comes in two different sizes, Miniature and Standard.
In a show ring, any dog that is six months or older that measures less than 10 inches or over 18 inches is to be disqualified. This is because Miniatures must be at least 10 inches tall but not more than 13 inches, and Standards must be over 13 inches, and up to (and including) 18 inches at the withers. In the United Kennel Club standard, a height over 19 inches is considered a fault.
The division into two size varieties is for conformation exhibition, and it should be noted that while one will find larger or smaller sizes, buyer beware. The Decker Rat Terrier, considerably taller at 18-23 inches, is not recognized by the AKC, UKC, FCI, Canadian Kennel Club, or any other major registry. There are other differences, as well. Rat Terriers have been around for a long time, while the Decker Rat Terrier came about during the 1970s. Their ancestries are different. The Rat Terrier Club of America offers a terrific visual aid in the form of a “family tree” on its website, and take note that the Basenji is not part of it, while it’s believed that a good dose of Basenji went into the development of the Decker.
Nor will one find the toy Rat Terrier in any of the aforementioned registries. Some sources write that in the 1920s, toy Fox Terriers that were too large were bred with Rat Terriers, resulting in toy-sized Ratties that came in between 8 inches to 12 inches in height.
Height is something of which to be aware if one is hoping to show and/or breed a Rat Terrier to meet its standard.