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The W58 was 15.6 inches (400 mm) in diameter and 40.3 inches (1,020 mm) long, with a basic weight for the warhead of 257 pounds (117 kg). The yield was 200 kilotons.
The W58 design entered service in 1964 and the last models were retired in 1982 with the last Polaris missiles.
Researcher Chuck Hansen claims based on his US nuclear program research that the W55 and W58 warheads shared a common primary or fission first stage; this design was nicknamed the Kinglet primary by Hansen in 2001.