Modern concepts in production management argue that it would be possibly preferable to instal a production rate which is fully synchronized with those rates of other production stages in the same firm or other firms. Thus, between the supplier and the customer of a finished or semi-finished product no inventory costs have to be taken into account, if the coordination will be perfect and JIT(Just-In-Time)-production takes place. Within a firm the synchronization may be a matter of planning and organization, and the kanban-principle is one possible result, though inventory is not really zero, but there exists always a buffer stock. As soon as two different firms are concerned, there are also different planning processes, and the advantage of the customer may become simultaneously the disadvantage of the supplier.