If the customer tolerance time is at least as long as the cumulative lead time, the product can be engineered, procured, produced, or delivered when actual demand in the form of a customer order is placed. Otherwise, all goods (such as semi-finished goods, single parts, raw materials, and information) from which the end product cannot be manufactured and delivered within the customer tolerance time must be ordered before there is known demand. The goods must all be procured and stocked on the basis of demand forecast. If the customer tolerance time is zero, the end
product must be procured before demand is known. This is the same as stocking the end product in a warehouse.