The B61 nuclear bomb is the primary thermonuclear gravity bomb in the United States Enduring Stockpile following the end of the Cold War. It is a low to intermediate-yield strategic and tactical nuclear weapon featuring a two-stage radiation implosion design.
The B61 is of the variable yield ("dial-a-yield" in informal military jargon) design with a yield of 0.3 to 340 kilotons in its various mods. It is a Full Fuzing Option (FUFO) weapon, meaning it is equipped with the full range of fuzing and delivery options, including air and ground burst fuzing, and free-fall, retarded free-fall and laydown delivery. It has a streamlined casing capable of withstanding supersonic flight and is 11 ft 8 in (3.56 m) long, with a diameter of about 13 inches (33 cm). Basic weight is about 700 pounds (320 kg), although the weights of individual weapons may vary depending on version and fuze/retardation configuration. As of 2020, it is undergoing a 12th modification. According to the Federation of American Scientists in 2012, the roughly 400 B61-12s will cost $28 million apiece.