The miniature Rat Terrier should weigh 10 to 18 pounds and should not be larger than 15 inches in height.
The toy Rat Terrier is an even smaller version of the breed. His weight should range between 5 to 10 pounds and he should be no larger than 12 inches in height.
In 1972, the first hairless Rat Terrier was born and from that little hairless female, a new strain of Rat Terrier was developed.