A barrel bomb is an improvised unguided bomb, sometimes described as a flying IED (improvised explosive device). They are typically made from a large barrel-shaped metal container that has been filled with high explosives, possibly shrapnel, oil or chemicals as well, and then dropped from a helicopter or aeroplane. Due to the large amount of explosives (up to 1,000 kilograms (2,200 lb)), their poor accuracy, and indiscriminate use in populated civilian areas (including refugee camps), the resulting detonations have been devastating. Critics have characterised them as weapons of terror and illegal under international conventions.