Ships in class: 13
The Acciao-class was the final subclass of the 600 Series. These boats were an improved version of the preceding Adua and Perla subclasses, and picked up an additional seventeen tons of displacement. The conning tower was lowered, giving it a less noticeable profile. The torpedo tubes and deck gun remained the same, but the 13.2mm machine guns were traded for a pair of 20mm cannons. Three of the boats eschewed aft torpedo tubes for more powerful engines. Thirteen Acciaios were built, eight of which were lost in action.