Grade: 25 Material: Stainless Steel (AISI 440) Diameter: 1/4, 0.25 inches (6.35 millimeter) Weight: 0.03601 ounces (1.021 grams) PGN’s G25 1/4" Stainless Steel Balls extremely precise and smooth surface guarantees you won't find any defects, such as flats, pits, soft spots, and cuts.