The W58 was an American
thermonuclear warhead used on the
Polaris A-3 submarine launched ballistic missile. Three W58 warheads were fitted as multiple warheads on each Polaris A-3 missile.The W58 was 15.6 inches in diameter and 40.3 inches long, with a basic weight for the warhead of 257 pounds. 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.
See more at Wikipedia.org...