The teeth of a bevel gear are arranged on a frustum of a cone, and they gradually taper from the larger end to the smaller end. Corresponding to the relevant "cylinders" in spur gears, such as the pitch cylinder, addendum cylinder, and base cylinder, in bevel gears these become "cones," such as the pitch cone, face cone, base cone, and addendum cone. Bevel gears are used to transmit power between two intersecting shafts. The angle of intersection Σ between the two shafts is called the shaft angle, and its value can be determined according to the transmission requirements, with 90° being the most commonly used.