O-Ring, No Metal Detectable, No X-Ray Detectable, System of Measurement Metric, Cross Section Shape Round, O-Ring Material Viton, Durometer (Hardness) Rating Medium Hard, Nominal Inside Dia. 21 mm, Nominal Width 3.5 mm, Actual Inside Dia. 21 mm, Actual Width 3.5 mm, Color Black, Durometer 75 Shore A, Nominal Outside Dia. 28 mm, Actual Outside Dia. 28 mm, Temp. Range -15 Degrees to 400 Degrees F, FDA Approved No