This bertha has been modified (repaired actually) to accept 24 mm motors. This brings new altitude possibilites to the Bertha, now capable of reaching 800 feet or so.  The higher impulse also allows this rocket to fly well in stronger winds, where the relatively weak C6 motors usually ended up with the rocket flying sideways into the wind.  Note also the black section just below the nose cone. This is an added payload, making this rocket 73mm longer than stock.