A seal is provided for preventing axial leakage through a radial gap between a stationary structure and a rotating structure. The radial gap is defined by an inner radial surface opposing an outer radial surface across the radial gap. The seal includes at least one land disposed on one of the inner radial surface and outer radial surface. At least one first tooth and at least one second tooth project from the other of the radial surfaces. The second tooth is shorter than the first tooth. At least one of the first tooth and second tooth, is configured to extend at an angle upstream. This angle is defined between a radial surface from which the first or second tooth projects and an upstream surface of the same tooth. The angle is less than or equal to about 80 degrees.