Abstract: A seal for preventing leakage around a rotary shaft extending through a structural casing comprising an annular stationary rigid seal secured to the structural casing for surrounding the rotary shaft. The stationary rigid seal has a smooth sealing surface for establishing a seal, and a resilient rotary seal adapted to be secured to the rotary shaft and having an annular projecting edge for contacting the smooth sealing surface under a biased pressure to form a seal in conjunction therewith. The projecting edge is formed by the convergence of inner and outer forward surfaces. A radial surface extends to the inner concentric forward surface from a torque point at its forward cylindrical base. An outer rearward surface extends to the outer concentric forward surface from a pivot point at its rearward cylindrical base. The outer forward surface forms an angle with the central axis of the seal in a plane through the central axis of the seal of from 40.degree. to 60.degree..