Grade: 25 Material: Chrome Steel (AISI 52100) Diameter: 5/16" Inches (7.9375 millimeters) Weight: 0.07250 ounces (2.055498 grams) PGN’s G25 5/16" Inch Chrome Steel Balls extremely precise and smooth surface guarantees you won't find any defects, such as flats, pits, soft spots, and cuts.