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 18 in Nominal Width 1/4 in Actual Inside Dia 17.955 in Actual Width 0.275 in Dash Number 465 Color Black Durometer 90 Shore A Meets/Exceeds ASTM D2000 NBR 90 Nominal Outside Dia 18 1/2 in Actual Outside Dia 18.505 in FDA Approved No