An inventory system combining features of the fixed reorder quantity inventory model and the fixed reorder cycle inventory model. Features of the fixed reorder cycle inventory model and the fixed reorder quantity inventory model can be combined in many different ways. For example, in the order point-periodic review combination system, an order is placed if the inventory level drops below a specified level before the review date; if not, the order quantity is determined at the next review date. Another hybrid inventory system is the optional replenishment model. Also see: Fixed Reorder Cycle Inventory Model, Fixed Reorder Quantity Inventory Model, Optional Replenishment Model.