 The P 6 class TB is larger than the P 4-class TB, with its size increased by 3 times and being more heavily armed, with two 21-in torpedoes replacing the 18-in torpedoes of the P 4-class, and twin 25 mm gun mounts replacing the 14.5 mm gun mounts of P 4-class.P 8-class torpedo boat is another development of P 6-class TB, which is a P 4-class with hydrofoil added.Although only a small number was built for the Soviet Navy, a large number of its derivative was built by Chinese as Type 025-class torpedo boat.