Abstract: A seal assembly for a valve stem has a primary seal ring with a relatively rigid gland member having an annular base of generally rectangular cross-section and a pair of flexible sealing lips formed in one piece with the base and extending outwardly from one side thereof. The sealing lips define a cavity for an elastomeric expander ring. The expander ring is disposed within the cavity and retained therein by the sealing lips. Each sealing lip has a sealing edge on the outer surface thereof which is pre-loaded against the valve stem and the valve housing when the primary seal ring is installed around the valve stem. Each sealing lip has a flared angle which narrows down to a thickness of between 0.033 and 0.041 inches along the length of the sealing lip between the base and the sealing edge.