This 90 durometer black nitrile (NBR) o-ring provides an increased hardness for tough applications. NBR o-rings offer the best combination of properties across a variety of o-ring applications. Nitrile compounds perform well in gasoline, crude oil, power-steering fluid, hexane, toluene, water, water-based hydraulic fluids, and dilute bases, such as sodium hydroxide. Because nitriles contain unsaturated carbon-carbon bonds in the base polymer, they are not suitable for exposure to ozone, sunlight, and weathering.