The FlaK 18 was mounted on a cruciform gun carriage that allowed fire in all directions, as opposed to split-trail designs, which allowed fire to the front only. The two "side" members of the carriage could be quickly folded up, allowing the gun to be lifted onto two wheeled chassis for high-speed towing. The weight of the gun meant that only large vehicles could move it, and the SdKfz 7 half-track became a popular partner. A simple "semi-automatic" loading system ejected fired shells, allowing it to be reloaded by operating a single handle and inserting a new shell. This resulted in excellent firing rates of 15 to 20 rounds a minute, perhaps double that of most weapons of the era. High explosive ammunition was used against aircraft and personnel, and armour-piercing and high-explosive anti-tank against tanks and other armoured vehicles.