In addition to the instrument settings, the filling level of the jar is crucial for the success of the grinding process in mixer jar mills. A jar filling should consist of about 1⁄3 sample and 1⁄3 ball charge (pieces). The remaining third is the free jar volume that is necessary for the free movement of the balls. Exceptions to this are voluminous materials, such as wool, leaves, and grasses. In these cases a material filling level of 70 to 80% is necessary.