Size Name:20 Balls Standard Diameter: 1/2′ / .50 InchesMetric Diameter: 12.7mmGrade: 1Material: Delrin PlasticBall Weight (each): .0515 Ounces / 1.46 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, low water absorption and is FDA approved. Naturally white in color it does accept opaque colors well and can be polished to a shine. Delrin is typically difficult to bond but can be bonded with epoxies, polyurethanes and cyanoacrylates (superglue). It has good chemical resistance but is sensitive to mineral acids, chlorine, and alkaline degradation. Common uses include; pump parts, valve bodies, and bearings.