A lot size that always uses the same quantity (or a multiple) for a reorder; the timing of the order varies while the size of the order is constant. Fixed lots are sometimes used when a process may require stamping out 100 pieces at a time, or when a vendor will only ship a carton of 500 items. Using fixed lots may mean placing fewer orders, at the tradeoff of carrying more inventory for a period of time than may be required.