Abstract: A two element, high and low pressure seal assembly to be used in a hydraulic or pneumatic sealing environment between two relatively movable machine parts, the seal assembly comprising an anti-extrusion spring element illustrated as generally rectangular in cross-section but including a projecting annular tongue and made of a relatively soft elastomeric material, the projecting tongue of said spring element contiguously engaging the entire surface of the base with the annular tongue being contained within an annular slot of a U-shaped elastomeric annular sealing member whereby the two member assembly functions jointly, and accommodates easy installation. The mating interface between the parts assure reliable unitary response but simultaneously provides a flex site at said interface which yieldingly resists imposed forces without fluid leakage. The U-shaped sealing element comprises a central body from which two anti-extrusion legs radially extend.