A minimum metal mine is a land mine that is designed to use the smallest amount of metal possible in its construction. Typically, the only metal components are located inside the fuze mechanism which triggers detonation. Both minimum metal anti-tank and anti-personnel mines exist. Some designs contain virtually no metal at all e.g. less than a gram. This is achieved by encasing the explosive charge in a plastic, wooden, or glass body, with metallic components limited to the few small parts in the fuze which can not easily be made from other materials, such as the spring, striker tip, and shear pin. Minimum metal mines are extremely difficult to detect using conventional metal mine detectors and usually require modern techniques, such as robotic Multi Period Sensing (MPS) equipment, to identify, but it is still too difficult to find non-metallic mines. These techniques are usually restricted to well-funded international mine clearing organizations and major militaries, making minimum metal mines especially pernicious where they are encountered.