Jack Russells are sturdy and tough, measuring between 10" and 15" at the shoulder. The body length must be in proportion to the height, and the dog should present a compact, balanced image. Predominantly white in coloration (more than 53%) with black and/or tan markings, they exhibit a smooth, broken or rough coat. The skin can sometimes show a pattern of small black or brown spots, referred to as "ticking", that do not carry through to the outer coat. All coat types should be dense double coats that are neither silky (in the case of smooth coats) nor woolly (in the case of rough coats). The head should be of moderate width at the ears, narrowing to the eyes, and slightly flat between the ears. There should be a defined stop at the end of the muzzle where it meets the head but not overpronounced, with a black nose. The jaw should be powerful and well boned with a scissor bite and very sharp teeth. The eyes are almond shaped and dark colored, and should be full of life and intelligence. Small V-shaped ears of moderate thickness are carried forward on the head. When the dog is alert the tip of the V should not extend past the outer corner of the eyes. The tail is set high and docked to approximately five inches in order to provide a sufficient hand-hold for gripping the terrier. It is a serious fault for the dog to have its tail down when in the show ring. The Jack Russell should always appear balanced and alert.