You can select the following standard item categories inside a bill of material (BOM):
Variable-size item: This item category is used for materials that have variable dimensions, such as pipes, wires, or fabrics. The system calculates the quantity of the variable-size item based on the formula and the dimensions entered in the BOM. You can also use the variable-size item to define a scrap percentage for the material.
Non-stock item: This item category is used for materials that are not managed in inventory, such as consumables, services, or subcontracting items. The system does not create any reservations or stock movements for the non-stock item. You can use the non-stock item to trigger purchasing requisitions or purchase orders for the material. References: Bill of Material Item Category; Bills of Material in Production Planning