52100 Chromium Steel Sphere, Grade G25, Mirror-Like Finish, Precision Tolerance, A295, 3mm Diameter, 0.0006mm Sphericity (Pack of 100) 52100 alloy steel provides high strength, high resistance to corrosion and wear, and good machinability Meets A295 specifications Meets grade 25 sphere tolerance Reflective finish provides a bright, mirror-like appearance Precision tolerance