A low viscosity, partially hydrogenated butadiene acrylonitrile copolymer designed primarily for dynamic applications requiring excellent resistance to heat, ozone and non polar hydrocarbon fluids. Sulfur curing systems are used for improved dynamic properties and adhesion to steel and textile reinforcing materials. However, peroxide/coagent systems can be used for improved resistance to heat and compression set. Low viscosity AT - technology provides a broad processing window, low mould fouling and the potential for higher filler loads compared to standard viscosity HNBR types.