Standard Diameter: 5/16" / .3125 InchesMetric Diameter: 7.9375mmGrade: 100Material: 440 Stainless SteelBall Weight (each): .072065 Ounces / 2.043 Grams440 stainless steel balls offer the precise geometry and fine surface finish that makes them especially useful for bicycles, casters, drawer slides, door locks and many other applications with the added benefit of corrosion resistance. 440 stainless steel is a high carbon martensitic stainless steel which has high strength, good hardness and wear