Nitrile, also referred to as Buna-N, rubber is one of many synthetic rubbers used to manufacture gaskets and seals. Nitrile rubber (also known as NBR) is a family of unsaturated copolymers of propenenitrile and certain butadiene monomers. Nitrile rubbers generally have good resistance to oil, fuel, diluted acids, alkalines and many other types of chemicals. A general rule of thumb is the more nitrile within a polymer, the higher its oil resistance. However the tradeoff will be a lower amount of flexibility.