Item Data Relevant to Material Items 
In the R/3 System, items in a material BOM tend to be material components. You use material numbers to identify these components.
See also:
Item Categories for Material Items
The following data is relevant to material items:
- Component
The system checks the material master in the plant in which you are maintaining the BOM. The system does not check plant data for a group BOM.
In certain situations, you do not need to enter a material number. For example, you can create a non-stock item without entering a material number.
- Component unit of measure
- For material components, you can maintain alternative units to the base unit of measure in the material master record.
In Bills of material, not all of these alternative units of measure are used. Only the unit of issue is relevant.
Possible values for the component unit of measure are therefore:
- Base unit of measure
- Unit of issue
- Units of measure that can be converted to the base unit of measure or unit of issue (same dimension)
- If you do not enter a unit, the system proposes a unit from the material master record, if the item has a material master record. If a unit of issue is entered on the storage detail screen of the material master, the system copies this unit to the BOM. Otherwise, the system copies the base unit of measure to the BOM.
- Units of measure without a dimension are only supported if they are identical to the stockkeeping unit or the unit of issue. You can define alternative units of measure in the material master.
- For non-stock items without a material master record, the system sets the value piece (PC).
In Customizing for Production, you can define which material types for BOM items can be combined with which material types for the BOM header and BOM usage in your company by choosing Bill of Material → Item data → Define allowed material types for BOM items.