The M18A1 was standardized in the early 1960s for use in the Vietnam War, and replaced the M18 anti personnel weapon. The M18A1 has a curved, olive coloured plastic casing, with the raised words 'Front Toward Enemy' moulded onto the convex side. Each Claymore is 21.5 cm long, 8 cm high, and 3.5 cm thick and come with two sets of adjustable legs. The weapon contains 650 grams of plastic explosive, fitted between a curved steel back plate and 700 steel ball bearings in front. It is equipped with a fixed plastic slit or knife edge sight (visible on the centre top), and two detonator wells (set at 45 degrees either side of the sight). When detonated, the steel balls have a lethal range of between 50 and 100 metres, but have been known to inflict injury up to 250 metres away. The weapon and all its accessories, including operating instructions, are carried in the purpose made M7 bandoleer.