Japanese Industrial Standard O-Rings are another popular classification system used around the globe. Published by the Japanese Standard Association, these o-rings are also categorized using the metric system. JIS O-Rings are used in many different fields, but typically are implemented in Japan's semiconductor, automotive and machine tool industries. Buna is also known as: Nitrile, NBR, N, Buna-N.

Nitrile, chemically, is a copolymer of butadiene and acrylonitrile. Acrylonitrile content is varied in commercial products from 18% to 48%. As the nitrile content increases, resistance to petroleum base oils and hydrocarbon fuels increases, but low temperature flexibility decreases.

Due to its excellent resistance to petroleum products, and its ability to be compounded for service over a temperature range of -65 to +275°F(-54 to +135°C), nitrile is the most widely used elastomer in the seal industry today.

Inherently nitrile does not possess good resistance to ozone, sunlight or weather, but this can be substantially improved through compounding. For more information, please see: Comparison Properties Chart, PTFE Encapsulated O-rings, Material Shelf Life, and O-ring Groove Design Chart.