A seal assembly for pressurized fluid applications, including supercritical fluid chromatography applications, includes an annular body and a helical wound flat spring. A bore extends through the annular body. The annular body has an outer lip and an inner lip opposed to and spaced apart from each other. The inner lip, outer lip and an overhanging lip portion of the outer lip define a pocket in which the helical wound flat spring is disposed. A load line of the helical wound flat spring is directed substantially along a direction of separation between the inner and outer lips to bias apart the lips. Embodiments of the seal assembly have an improved distribution of contact pressure between the inside diameter of the seal assembly and the plunger with which the inside diameter seals, and between the outside diameter of the seal assembly and a gland surface with which the outside diameter seals.