In spite of the enormous advantage attributed to JIT, most of its adopters embrace it only partially. many companies that are considered users of jit purchasing handle only a small percentage of their materials requirements by jit methods.Among the reasons are 1 the time and effort required to convert many suppliers to a jit shipping pattern, 2 the difficulty of obtaining shipping at a cost low enough to justify many small deliveries, 3 the likelihood of occasional shipping delays if suppliers are hundreds of miles away,and 4 the frustrating tendency for a low-cost,allegedly noncritical part to become critical when it does not arrive on time and an important customer's order cannot be finished because there is no safety stock. For these and other reasons,some companies claim to have adopted just in time but continue to keep safety stock of many materials"just in case" For example,it has been reported that the Nissan truck plant in Smyrna,Tennessee, has only one true jit material-seats, delivered daily by a single supplier with no safety stock ever held.Some other materials are quasi-JIT,being delivered twice per week;but a sizable percentage of all parts are still supplied in large lots as in any traditional purchasing system.