Service Parts Stock Management is a part of the service process to ensure that right spare parts are in the warehouse at the right place and time, with respect to a customer demand. Customer satisfaction can be measured through the First Fill Rate Value (FFRV). The FFRV optimization is an inventory planning problem, which can be formalised through a stochastic linear programming problem and evaluated for different spare parts or sets of them, considering production and cost constraints. In this paper the problem and the details of the proposed approach will be discussed and assessed through some experimental data.