The device detonated in the Mike test, called the Sausage, was the first "true" H-Bomb ever tested, that is - the first thermonuclear device built upon the Teller-Ulam principles of staged radiation implosion. The device was designed by the Panda Committee directed by J. Carson Mark at Los Alamos (Teller declined to play a role in its development).

The 10.4 megaton device was a two stage device using a TX-5 fission bomb as the primary stage, and a secondary stage consisting of liquid deuterium fusion fuel stored in a cylindrical Dewar (thermos) flask. Running down the center of the Dewar was a plutonium "spark plug" rod to ignite the fusion reaction. The Dewar was surrounded by a natural uranium pusher/tamper weighing more than 5 metric tons. The entire assembly was housed in an enormous steel casing, 80 inches wide and 244 inches long, with walls ~10-12 inches thick, the largest single forging made up to that time. The inside surface of the casing was lined with sheets of lead and polyethylene to form the radiation channel that conducted heat from the primary to the secondary. The entire device weighed 82 tons.

The enormous explosion was the 4th largest device ever tested by the U.S. 77% (8 megatons) of the yield was due to fast fission of the natural uranium pusher/tamper, with remainder (2.4 megatons) coming directly from fusion of the deuterium fuel. The island the test device was installed on, Elugelab (code named Flora), was entirely destroyed. The resulting crater was 6240 ft across and 164 ft deep. High levels of radiation blanketed much of the atoll following the test.