The 1954 series of high-drag bombs was built in six sizes: 250 kg (550 lb), 500 kg (1,100 lb), 1,500 kg (3,300 lb), 3,000 kg (6,600 lb), 5,000 kg (11,000 lb), and 9,000 kg (20,000 lb). A feature of the 1954 series of bombs is the ballistic ring on the nose of the bomb which acts as a vortex generator to aid the bombs stabilizers. The smaller (less than 3,000 kg) bombs had a single nose and a single tail fuze, while the larger weapons shared a single nose fuze and two base fuzes. The FAB-9000 (9,000 kg/20,000 lb) weapon was roughly comparable to the wartime Grand Slam bomb. It was used by Russian aircraft designers as a substitute for early nuclear weapons when determining the size and clearances of bomb bays.