The protective jaws have a strong base body made of aluminum or are completely made of polyurethane (type PP and type PR), the profile is right-angled and plane-parallel; the high accuracy of the vise is maintained, the integrated special magnets hold the protective jaws securely to the vise, despite extremely high magnetic force, the magnetism does not penetrate to the clamping surfaces, so that neither an attraction of chips nor a magnetization of the workpieces occurs