The term load washers refers to a specialty version of a disc spring or Belleville washer used to improve security of a bolted connection. They prevent a loosening of the connection by e.g. setting losses in that their own spring load can maintain the initial load of the connection. This makes them very suitable for mostly axially loaded short screws. They are not effective against coming loose due to changing cross loading. It could be made from M2 to M30.