This article focuses on the monitoring of a supply chain dedicated to a mass production of strongly diversified products and more particularly in the part of this chain which contributes to the production of a set of alternate modules assembled on a work station of the assembly line. The approach of the MRP is adopted in the monitoring of that chain but the distance of the production units leads to a mixing between production to stock and production to order. The literature available on safety stock does not help in decision making. The relation that exists between frozen horizon and Order Penetration Point in MRP will be examine and the analytical relations which links planned orders of a reference to the requirements of the MPS which uses them, is established. Then we set the relations which make it possible to define, in the steady state, the quantities to produce to cope with requirements that are partially or completely random, taking into account or not the problem of quality, in order to limit the stockout risk to a predetermined level
