*This product is a Noltlock iron material washer. Noltlock washers are high quality products that have proven success in many industries. Noltlock washers are generated energy, transportation, oil field mining (offshore), mining and quarring, construction and cross-linking. Used in a variety of industries including manufacturing and processing, shipbuilding, agriculture, large transportation equipment, military. Noltlock washers do not only provide a secure loosening feature, but also allow the overall performance of the bolt fastening.