Standard Diameter: 5/8" / .625 InchesMetric Diameter: 15.875mmGrade: 1Material: Delrin PlasticBall Weight (each): .09876 Ounces / 2.80 GramsDelrin (Polyoxy-Methylene), also known as Acetal, Polyacetal, and POM, is an engineering thermoplastic commonly used for precision parts that require high strength, hardness and rigidity. It is a tough material with a low coefficient of friction and high abrasion resistance. It has good electrical and dielectric properties and low water absorption. Naturally