This metric O-ring is made of red silicone, has a durometer of 7OA, a round cross-section, and can be used across a wide temperature range (from -65 degrees F/-51 degrees C to 450 degrees F/232 degrees C). Designed for use in a wide variety of sealing applications, this silicone O-ring meets standards defined by Aerospace Standard AS568A, which is the Aerospace Size Standard for O-rings. Silicone is resistant to ozone, weather, detergent, salt water, engine and transmission oil, non-petroleum brake fluid, hydraulic fluids that resist fire, vegetable and animal oils, and high molecular weight chlorinated aromatic hydrocarbons. Silicone is vulnerable to mechanical wear and tear, water and steam over 250 degrees F/121 degrees C, aromatic hydrocarbons (benzene), chlorinated hydrocarbons (trichloroethylene), acids and bases, and hydrocarbon fuels. The durometer hardness of this silicone O-ring is 70A. 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.