During World War II, Italian torpedoes were designated as follows: Initials of the builder, warhead weight and overall diameter and length. Sometimes there was also a particular mark added. The principal builders were Whitehead (W) at Fiume (usually called just "Fiume") and Silurificio Italiano (SI) at Naples (usually called just "Naples").
For example, W270/533.4 x 7.2 "F" meant that this torpedo was built by Fiume (Whitehead), with a 270 kg (595 lbs.) warhead, was 533.4 mm (21") in diameter, 7.2 meters (283") long and was model "F" of that type.
Except for some special, circling, electric airborne torpedoes, torpedoes built during World War II were wet-heater systems using natural air and kerosene type fuel. In old torpedoes, the engine was a four-cylinder Brotherhood type radial. Later Fiume ones had a two-cylinder horizontal double-acting engine. The Naples torpedoes had a two-row eight-cylinder radial except for the latest ones, which had a eight-cylinder in-line engine. It is believed that Naples also considered a V-12 engine.
During World War II, older torpedoes used Whisker impact pistols. Newer ones used a two inertial pendulum type that would fire on impact, even at fine track angles and at low speeds, the limit claimed being 15° and 5 knots. A magnetic pistol based on a coil without the usual rod was developed. This pistol was also used by the Germans, who considered it to be less liable to perturbations than their own coil rod and amplifier design.