The W88 is an American thermonuclear warhead, with an estimated yield of 475 kilotons of TNT (1,990 TJ),[2] and is small enough to fit on MIRVed missiles.

[8] In 1999, the San Jose Mercury News reported that the W88 had an egg-shaped primary and a spherical secondary, which were together inside a radiation case known as the "peanut" for its shape.

[Note 1] Four months later, The New York Times reported that in 1995 a supposed double agent from the People's Republic of China delivered information indicating that China knew these details about the W88 warhead as well, supposedly through espionage (this line of investigation eventually resulted in the abortive trial of Wen Ho Lee).

If these stories are true, it would indicate a variation of the Teller-Ulam design which would allow for the miniaturization required for small MIRVed warheads.

[10][11][12] The value of an egg-shaped primary lies apparently in the fact that a MIRV warhead is limited by the diameter of the primary—if an egg-shaped primary can be made to work properly, then the MIRV warhead can be made considerably smaller yet still deliver a high-yield explosion—a W88 warhead manages to yield up to 475 kt with a reentry vehicle length of approximately 60 inches (1,500 mm) and base diameter of 18 inches (460 mm) while the actual physics package is 35 inches (890 mm) long.