Collies are generally medium-sized dogs of about 10 to 25 kg (22 to 55 lb), fairly lightly built with a pointed snout and erect or partly erect ears, giving a foxy impression. Cattle-herding types tend to be rather more stocky. Collies are always alert and are active and agile. The fur may be short, flat, or long, and the tail may be smooth, feathered, or bushy. Working collies are extremely energetic and agile dogs with great stamina, well able to run all day without tiring, even over very rough or steep ground. Working collies are of excellent working/obedience intelligence, and are instinctively highly motivated to work.