Nowadays, the inventory management is a central issue for companies. On the one hand, having too high stock levels in spite of the real requirements may lead to circulating capital's immobilization; on the other hand, low stock levels may cause lost of sales and consequent customer dissatisfaction. The aim of this paper is the definition of a model based on a customized AHP (Analytic Hierarchy Process) model for evaluating the optimal procurement policy regarding standard items (screws, bolts, screw nuts, etc.). These items are the last sub codes within complex bill of materials (BOM) for products manufactured by an important make to order company. This model allows to assign to each BOM items the right management inventory policy, depending on their priority and criticality according to the customer requirements.