These rivet sets are free from any machine marks and ridges and meet exact tolerances for each rivet size and type. Manufactured from high-grade shock-resistant tool steel and machined in accordance with MIL-STD GGG-R-425. Each set is part number stamped with the rivet size, safety notice and "Made in USA". Each set is plastic coated to preclude damage during shipping and storage. The manufacturing of these sets incorporate proper distribution of mass and correct grain during the forging process. Correct heat-treating provides a high-quality product that will provide you the most service life of any tool.