The present invention provides a process of hydrogenating a nitrile copolymer rubber, which comprises subjecting the copolymer to hydrogenation in the presence of a hydrogenation catalyst, a co-catalyst, and a proton acceptor that is non-coordinating with the metal-complex catalyst. A first securing arrangement secures together opposite ends of the neck strap about the person’s neck. Thus, the liner reduces the destructive cutting away of the fan case, minimizing damage to the fan case and decreasing torque loading of the fan case from rotor deflections.