Submarines of this type served in the German (UB-1 class), Austro-Hungarian (U-10 class) and Bulgarian navies. Preceded by the UA and succeeded by the UB II class (SM UB-18-47). Building ordered on 15 October 1914, laid down by AG Weser, Bremen, Germany with yard number 223 on 9 November 1914, launched on 23 March 1915, commissioned on 25 March 1915, disarmed on 25 November 1918 and scuttled in the Black Sea off Sevastopol, Russia in first half of 1919.
General technical class characteristics. Displacement 127 (surfaced)-142 (submerged) tons and as dimensions 23,62 (pressure hull)-27,88/28,10 (over all) x 3,15 x 7,30 (depth) x 3,03 (draught) metres or 77.6-91.6/92.2 x 10.4 x 23.11 x 9.11 feet.. The machinery consisted of 1 diesel engine and 1 electric motor driving one screw allowing a speed of 6,47 (surfaced)-5.5 (submerged) knots and a surfaced range of 1.860 nautical miles with a speed of 5 knots and submerged 45 nautical miles with 4,5 knots. Test depth 50 metres/160 feet and able to dive within 33 seconds. Their crew numbered 14 men. The armament consisted of 2-45cm/17.7” torpedo tubes in the bow for which 2 torpedoes were carried and 1-0,8cm/0.31” machinegun.