A BOM is a listing of all materials for a given product; however, a single product might have many variations in which the individual list of materials varies. These variations can be as simple as differing colors for individual colorways, in which the materials are the same, but the coloring of the material for different colorways is different. Variations can also be much more complex, such as materials that vary based on the factory in which the product is produced, or the sizes that a product is produced in. A factory may source materials from different locations, located nearby to their facility, and a larger size might require an elastic or use different shoulder pads. Quantities for materials may also vary based on size.

When you create the top (product) level BOM, it contains the list of components that make up the given product. Assigning material, quantity, color, or any other pertinent information at the top level means that this information applies for any way the product is built. Applying an override for a given variation (or combination of variations) means that there is a variation in the manner in which the product is built for that variation.

PTC FlexPLM allows you to create BOM overrides within the BOM editor. Once the main BOM has been created, you can create all possible overrides in that main BOM without having to create a new BOM for each override. To do this, click Variations on the Edit BOM page. You can select any combination of variations and apply your overrides to that particular variation of the BOM.

The top-level BOM only requires one component to apply overrides. Adding a material and a supplier to the component, as well as selecting a color means that the selected material, supplier, and color apply for the given component across all BOM variations. This component always uses the given material, from the given supplier, and is always the given color.