The Type 404 multi-purpose tender Main recently completed modernization to become Germany's newest submarine tender and supply vessel . The modifications made at Elsflether Shipyard took approximately one year. Improvements include the addition of torpedo storage and handling room for up to 16 torpedoes, a diving chamber for eight divers, and a fueling station for the diesel, oxygen, and hydrogen used on board German submarines. To better support boats tying up alongside, fenders have been added to both port and starboard sides amidships. Two MLG 27-mm naval guns have been fitted to provide an improved close-in defensive capability. New electronics include retractable bow sonar, an underwater telephone, and an advanced Automatic Identification System to improve collision avoidance and navigation while assisting with the tracking of naval assets. Though modifications are extensive, dimensions and full-load displacement remain unchanged at 100.58 meters and 3,590 tons, respectively.