These are all inert PMA-3 Minimum Metal Anti-Personnel Mines. 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.