Domestic Medium Hair is a coat description, not a breed. It covers mixed-ancestry house cats with fur longer than a shorthair's but without a longhair's heavy ruff, often with a plumed tail, tufts between the toes and a soft undercoat. They come in every color and pattern, and most are medium-sized, weighing roughly 6 to 14 pounds.
Size, personality and health depend on each cat's mixed background, age and early experiences, so meeting a cat matters more than reading its label. Many are adaptable and affectionate, and a good number live well into their teens. Plan on regular brushing, with extra sessions when the coat thickens in fall and sheds in spring, and on keeping your cat indoors.