This O-ring is made of black Aflas (fluoroelastomer) and has a durometer of 80A. It has a round cross-section and can be used across a wide temperature range (14 degrees F/-10 degrees C to 428 degrees F/220 degrees C). Designed for use in a wide variety of sealing applications, this Aflas O-ring meet standards defined by Aerospace Standard AS568A, which is the Aerospace Size Standard for O-rings. Aflas (fluoroelastomer) is resistant to oil, heat, electricity, abrasion and many chemicals including strong acids and bases. It is also performs well in all-weather, ozone, and steam applications, although it performs poorly in aromatic hydrocarbons or ketones. The durometer hardness of this Aflas O-ring is 80A. Durometers measure the hardness of a material and its resistance to permanent indentation. A higher durometer value indicates greater resistance to indentation. On a scale of 0 to 100, a value of 0 indicates that a sample was completely penetrated, while a value of 100 shows no indentation in the sample. The letter following the number identifies the shore scale, which is either shore A or D. Shore A is used for softer plastics, while shore D is used for harder plastics. O-rings provide a pressure and fluid seal between cylindrically shaped, overlapping mating surfaces and are commonly seen in engines, faucets, flanges, valves, and various cylinders. They are circular in shape, with a round cross section, and a hole in the center, similar to a doughnut. O-rings are available in various AS568A dash sizes, which is the standardized sizing for O-rings, and defines the nominal inside diameter (ID), outer diameter (OD), and cross-sectional (CS) diameter of an O-ring.