This NBR - Nitrile O-Ring has a diameter of 50.4x3.53 mm and is Black in color. The hardness of this O-ring 50.4x3.53 - NBR - Nitrile - 70 Shore A - Black - FDA / NSF61 - ORS171998 is 70 Shore A. Alternative names for the compound are Nitrile Rubber - NBR, and it is commonly produced by Lanxess - Zeon - and LG Chem. The O-Ring is typically used in and has an operating temperature range from -30 ºC to 135 ºC. O-Rings 1297275 are referred to as 171998 and have a DIN 3771 size of 50.4x3.53. This item is equivalent to and has an FDA approval. The chemical name of this O-Ring is Acrylonitrile butadiene rubber.