## mBOM

The mBOM is a part’s planned parts list. See [Bills of materials overview](https://docs.firstresonance.io/build-hardware/bills-of-materials) for how it relates to the aBOM and build requirements. This page covers building and consuming it.

## mBOM line items

The mBOM table shows these columns per build requirement line:

| Column | Notes |
| --- | --- |
| **Part Number / Rev** | The required part, shown with its revision |
| **Quantity** | How many of the part go in. Multiplied by the parent’s run quantity at execution time |
| **Substitutes** | Approved alternate parts. See [Alternates and substitutes](https://docs.firstresonance.io/build-hardware/bills-of-materials/substitutes) |
| **Reference Designators** | Positional identifiers such as `R12`, `U7`, and `Q1`. See [Reference designators](https://docs.firstresonance.io/build-hardware/bills-of-materials/reference-designators) |
| **Made on Assembly** | Whether this part is built directly onto the parent. See [Made on assembly](https://docs.firstresonance.io/build-hardware/bills-of-materials/made-on-assembly) |

For the GraphQL shape, see [mBOMs API](https://docs.firstresonance.io/api-reference/guides/mboms).

## Creating an mBOM

1. Open the parent **part** in the Parts Library.
2. Find the **mBOM** card on the part page. If the part has no mBOM yet, click **Create mBom**.
3. With the version in **Draft**, click **New Part** and pick the child part. ION adds a line with a quantity of 0.
4. For each line, set the **Quantity** and optionally add substitutes, reference designators, and the **Made on Assembly** checkbox directly in the row.

Edits save as you make them; there’s no separate save step. mBOM lines are editable only while the version is in **Draft**. For version states and the release flow, see [Manage BOM versions](https://docs.firstresonance.io/build-hardware/bills-of-materials/versions).

The mBOM card on the part page is a quick editor. For the full mBOM, including its complete version history, use the **Go to full mBom** link in the card header.