This NBR - Nitrile O-Ring has a diameter of 56.87x1.78 mm and is Black in color. The hardness of this O-ring 56.87x1.78 - NBR - Nitrile - FDA - NSF 61 - 70 Shore A - Black - ORS221957 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 6590099 are referred to as 221957 and have a DIN 3771 size of 56.87x1.78. This item is equivalent to and has an FDA - NSF 61 approval. The chemical name of this O-Ring is Acrylonitrile butadiene rubber.