Abstract: A rod or piston primary seal, which includes a primary seal (2) facing the space (1) to be sealed and a secondary seal (3) facing away from it, in which the primary seal (2) is fitted into the groove (4), of a holding element (5), open in the direction of the relatively movable machine part (11) which is bounded, on the side facing away from the space (1) to be sealed, by a first side surface (7) which extends essentially at right angles to the sealing axis (6), and includes a sealing edge ring (8) made of tough, hard plastic which has a sealing edge (9) lying adjacent to the machine part (11) and is pressed with its sealing edge (9) onto the machine part (11) by a profile ring (10) made of elastomeric material which is supported on the bottom surface (12) of groove (4) and lies adjacent to sealing edge ring (8) with its inner surface (13), the sealing edge ring (8) having a profile bounded essentially by a right angle between the sealing edge (9) and the bounding surface (14) facing the first side surface (7