A braking band of a disc for a disc brake of the ventilated type, unusually capable of improving the disc cooling efficiency, extends between an inner diameter close to an axis of rotation of the disc and an outer diameter away from the said axis of rotation of the disc. The braking band may have two leaves defining an intermediate space and joined by a connection. The ratio between the outer diameter of the surface and the thickness or maximum dimension of the said intermediate space between the two leaves measured in a direction parallel to the axis of the disc may be between 15 and 32.