Today, excellence in production planning and control (PPC) is not only critical for the success of enterprises it is rather a strategic factor of competitiveness. Particularly in job shop manufacturing lot sizing is a vitally important function of PPC, due to its influence on the necessary positioning between manufacturing efficiency on the one hand and flexibility on the other hand. The article shows by example of a project of the IFA and the proIng GbR in cooperation with an automotive components supplier, that the development of a concept for effective an efficient lot sizing requires in addition to the selection of the suitable method a logistical analysis and classification of the products.