The coupling head has a rubber seal (2) that is arranged in a piston (1) of a compressed air line. A stiffener (3) is arranged on inner periphery of the rubber seal extending over complete inner periphery. The rubber seal is designed cylindrically and is arranged together with the cylindrical stiffener inside the piston, where the piston has annular, saw-tooth like recesses (5) to seal the compressed air line and to fix the rubber seal by contact of annular stampings (4) with the inner periphery of the piston.
