Domestic Medium Hair is a coat description rather than a breed. Shelters use it for mixed-ancestry cats whose fur falls between short and long: fluffier than a domestic shorthair, often with a plumed tail, tufts between the toes and a soft undercoat, but without the heavy ruff of a true longhair. They turn up in every color and pattern, from tabby and tuxedo to calico and solid black.
Most adults weigh 6 to 14 pounds and live 12 to 18 years. Size, personality and health depend on each cat's ancestry and history, not a breed standard, so two cats with the same coat can act very differently. Expect more brushing than a shorthair needs, especially in spring and fall, and plan on a home where the cat can stay indoors.