a blow molding machine for containers , having a conveyor path carrying a mandrel holder and pre - forming mandrels attached to the mandrel holders in an exchangeable manner by means of removable couplings , wherein each coupling has a mandrel clamping mechanism and a releasing element accessible form outside that can be adjusted at least relative to the mandrel holder for releasing the clamping mechanism . in the mandrel holder , particularly for use in a blow molding machine , the mandrel clamping mechanism is designed with a ball joint lock , and the ball joint lock can be released by means of a releasing element in order to exchange a performing mandrel .