The larger boat was to not to exceed 80 feet and to carry at least two 21-inch torpedoes, four depth charges, and two .50-cal machine-guns. The performance specification was to achieve 40 knots and an operating radius of 275 miles at top speed (550 miles at cruising speed) The smaller boat was to weigh no more than 20 tons so that it could be easily transported by cargo ships. Its maximum speed was also 40 knots but specified radius was 120 miles at top speed and 240 miles at cruising speed. Armament was less - two torpedoes and depth charges, or .50-cal machine-guns and a smokescreen generator.