Abstract: A seal element for installation in an annular groove having a mouth, first and second radial surfaces, and an axial surface therebetween. The seal element has a first radial surface which forms an acute heel angle with the groove first radial surface, and the seal element forms an inner static area adjacent the groove axial surface and first radial surface. Upon installation of a rod and low pressure application, the seal element is compressed into the groove, and the seal element first radial surface is moved into contact with the groove first radial surface. Thus, the seal element prevents contamination from entering into the inner static area. The seal element has first and second angled surfaces forming a high pressure sealing line and third and fourth angled surfaces forming a low pressure sealing line with a stress-relieving radius interconnecting the second and third angled surfaces.