Variable yield—or dial-a-yield—is an option available on most modern nuclear weapons. It allows the operator to specify a weapon's yield, or explosive power, allowing a single design to be used in different situations. For example, the Mod-10 B61 bomb had selectable explosive yields of 0.3, 5, 10 or 80 kilotons, depending on how the ground crew set a dial inside the casing when it was loaded onto an aircraft. Variable yield technology has existed since at least the early 1960s. Examples of variable yield weapons include the B61 nuclear bomb family, B83, W80, W85, and WE177A warheads.