Because it is a purchase order. As a result, fewer orders at a time. How much less, so we need to wait to purchase raw materials, along with the other versions, so that the minimum amount sufficient.
Because the order As a result, the number of orders per session. A small number, so we need to wait for purchase along with other models to meet the minimum amount.
Due to the order. The resulting order per time a small number. A small number, so we need to wait for the purchase of raw materials, along with the other models to the adequate to the minimum.