Alternative Items 
Use this window to define alternatives for items that are out of stock in a certain warehouse. Alternative items are defined by item. You can build a hierarchy of alternative items by defining alternatives for the alternatives.
When creating business documents, open the list of alternative items and replace the item that is out of stock.
Recommendation
Do not use an alternative item as a component of a BOM-related product.
Example
This example provides a business scenario to demonstrate why it is not recommended to use an alternative item in a BOM-related product.
During production of a BestPhone cell phone, the BestPhone battery unit is not available, and a different brand battery is used. A consumer purchases one of these BestPhone cell phones over the counter, and discovers later that the battery is not the BestPhone brand that he or she had assumed was in the cell phone, and returns the product for a refund.