O-Ring No Metal Detectable No X-Ray Detectable System of Measurement Inch Cross Section Shape Round O-Ring Material Buna N Durometer (Hardness) Rating Very Hard Nominal Inside Dia 17 1/2 in Nominal Width 1/4 in Actual Inside Dia 17.455 in Actual Width 0.275 in Dash Number 464 Color Black Durometer 90 Shore A Meets/Exceeds ASTM D2000 NBR 90 Nominal Outside Dia 18 in Actual Outside Dia 18.005 in FDA Approved No