Kinglet was a boosted fission primary used in several American thermonuclear weapons.
[1] The W55 warhead for the UUM-44 SUBROC anti-submarine missile and the W58 warhead for Polaris A-3 were designed to use Kinglet, while the W47 warhead for Polaris A-1/A-2 were retrofitted with Kinglet to overcome the technical issues with the Robin primary the W47 was initially deployed with.
[2][3] Allegedly, only the W47Y2[a] was converted to the Mod 3 design using Kinglet.
[4] The Kinglet device was approximately 11.2–11.57 inches (284–294 mm) in diameter, 11.5–12.2 inches (290–310 mm) in length and weighed approximately 58–63 pounds (26–29 kg).
Two-point devices only require two detonators to fire the whole device, compared to earlier nuclear weapons that required tens of detonators.