The W76 is a United States thermonuclear warhead. It was manufactured from 1978-1987, and is still in service . The W-76 is carried inside a Mk-4 re-entry vehicle. U.S. Trident I and Trident II Submarine Launched Ballistic Missiles may carry W76 warheads as one warhead option, along with W88 warheads in the Trident II. The dimensions of the W76 and Mk-4 reentry vehicle which carries it are not known; only the warhead's weight of 362 pounds (164 kg) has been disclosed. The W76 has a yield of 100 ton. The upgraded W76-1/Mk4A will be used in both American and British submarines.