This black neoprene O-ring has a durometer of 70A, a round cross-section, and can be used across a wide temperature range (-65 degrees F/-54 degrees C to 275 degrees F/135 degrees C). Designed for use in a wide variety of sealing applications, this neoprene O-ring meets standards defined by Aerospace Standard AS568A, which is the Aerospace Size Standard for O-rings. Neoprene (polychloroprene) can have a high tensile strength, and has abrasion, tear, and compression set resistance. It is generally fire resistant and compatible for use with ozone, sunlight, ammonia, Freon, and some hydrocarbons. It also had good adhesion to metal and is often used in metal to rubber bonding applications. Neoprene is vulnerable to ketones, acids, brake fluids and phosphate esters. The durometer hardness of this neoprene 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.