Special objects shipyard) in Split, the new class featured a streamlined hull design and four bow facing torpedo tubes that could also be used for minelaying.

With the start of the Croatian War of Independence all three boats were relocated from the Lora Naval Base to Montenegro where they were commissioned with the SR Yugoslav Navy.

Travelling underwater using a snorkel at a speed of 10 knots (19 km/h; 12 mph), the boats had a range of 4,100 nmi (7,600 km; 4,700 mi).

Before being officially commissioned with the Navy, Heroj underwent a series of sea trials in order to test the maximum operational parameters of the submarine.

This in turn affected the hydrodynamics by creating a positive trim and surfacing the submarine at high speed within seconds.