The G7a (TI) was the standard issue Kriegsmarine torpedo introduced to service in 1934. It was a steam-powered design, using a wet heater engine burning decaline, with a range of 7,500 metres (24,600 ft) at 40 knots (74 km/h; 46 mph) speed. In 1936, the Kriegsmarine's first electrical powered torpedo was introduced with the G7e(TII). It was replaced beginning in 1942 by the G7e (TIII). The G7a(TI) remained in service as the main torpedo of Kriegsmarine for the length of the war, being the only torpedo used from surface vessels, and alongside electric torpedoes on the uboats. The G7a(TI) torpedo was 533.4 mm (21.00 in) in diameter, 7,163 millimetres (23 feet 6.0 inches) in length (with a type Ka or Kb warhead and Pi1 or Pi2 pistol), the warhead holding a charge of approximately 280 kg (620 lb) of so-called Schießwolle 36. It was Kriegsmarine's first operational torpedo (hence TI = Torpedo number one), and the standard issue torpedo for all German U-boats and surface torpedo-bearing vessels from 1934 to the end of WW2.