Serrated Washers available in mm and inches, which have internal teeth, are available in Stainless Steel, Plated Steel, or Phosphor Bronze as standard. These "shake-proof" serrated washers fitted internally to the equipment, before the application of a locknut act as an anti-vibration device to prevent the cable gland and locknut arrangement from loosening in service. These are of particular importance in situations where vibrating heavy machinery, such as mud shakers, pumps and drilling equipment is operating aboard mobile or fixed onshore and offshore drilling units.