Grade: 25 Material: Chrome Steel (AISI 52100) Diameter: 5/8" Inches (15.875 millimeters) Weight: 0.58004 ounces (16.44399 grams) PGN’s G25 5/8" Inch Chrome Steel Balls extremely precise and smooth surface guarantees you won't find any defects, such as flats, pits, soft spots, and cuts.