They are the first submarines in the world to feature a Stirling engine air-independent propulsion (AIP) system, which extends their underwater endurance from a few days to weeks.

While submerged, the Kockums-built Stirling engine AIP system is used to drive a 75-kilowatt (101 shp) generator for either propulsion or charging the batteries.

The X rudder provides four control surfaces, along with two mounted on the sail, which enables sharp turns and the ability to operate very close to the seabed.

Its magnetic signature is counteracted by 27 independent electromagnets, short-circuiting extremely low frequency (ELF) electrical fields.

[3] After being refitted and upgraded to sustain the higher temperatures of tropical water,[4] HSwMS Halland took part in a multi-national exercise in the Mediterranean from September 16, 2000.

[4] In 2004, the Swedish government received a request from the United States to lease HSwMS Gotland – Swedish-flagged, commanded and manned, for one year for use in antisubmarine warfare exercises.

[10] In 2005, HSwMS Gotland managed to snap several pictures of USS Ronald Reagan during a wargaming exercise in the Pacific Ocean, demonstrating that it was in a position to sink the aircraft carrier.

[12][13] In 2001, during the exercise JTFEX 01-2 in the Caribbean Sea, the German U24 of the conventional 206 diesel-electric class "sank" the carrier Enterprise by firing flares and taking a photograph through its periscope.