Mark 7 "Thor" (or Mk-7')was the first tactical nuclear bomb adopted by US armed forces. It was also the first weapon to be delivered using the toss method with the help of the low-altitude bombing system (LABS). The weapon was tested in Operation Buster-Jangle. To facilitate external carry by fighter bomber aircraft, Mark 7 was fitted with retractable stabilizer fins. Mark 7 was a dial-a-yield capsule-type weapon with fissionable elements (uranium 235) stored in a separate container. The Mark 7 warhead (W7) also formed the basis of the 30.5 inch (77.5 cm) BOAR rocket, the Mark 90 Betty nuclear depth charge, and MGM-5 Corporal and MGR-1 Honest John ballistic missiles. It was also supplied for delivery by Royal Air Force Canberra aircraft assigned to NATO in Germany under the command of SACEUR. The Mark 7 was in service from 1952 to 1968 with 1700-1800 having been built.