> ## Documentation Index
> Fetch the complete documentation index at: https://docs.firstresonance.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Enable mBOM version selection

> Let a procedure pin the mBOM version it assigns from, and require a pin before the procedure can be reviewed or released.

This setting decides whether the mBOM version pinned to a part governs the procedure that assigns from it. It's independent of [Enforce mBOM parts assigned to steps](/administration/production-settings/enforce-mbom-parts-assigned-to-steps), so you can turn either one on without the other.

## Enable mBOM version selection

1. In ION, go to **Settings > Production > Procedures**.
2. Turn on **Enable mBOM version selection**.

## What the setting changes

With the setting on:

* Every part must be pinned to a specific mBOM version before a procedure can be sent for review or released.
* New runs follow the pinned version instead of the latest released one.
* The **mBOM** row in the procedure's **Assigned Parts** section carries the version picker and the pin controls. See [Switch the pinned mBOM version](/build-hardware/procedures/installation-requirements-beta#switch-the-pinned-mbom-version).
* Creating a new mBOM revision stops copying part-step assignments onto the new revision for procedures that pin the part, because a new revision is born in draft and an assignment on it would be unreachable.
* Assigning a sub-assembly's components needs that sub-assembly's own pin first, which you set when you assign the sub-assembly in the procedure's right rail.

With the setting off, a pin recorded on a part is ignored and the part's latest released mBOM version governs everywhere, so assignments carry forward to a new revision as before.

<Note>
  A draft mBOM version never governs. A part whose only version is unreleased has no governing version at all, in either setting state, so there is nothing to assign from until you release a version.
</Note>

## Related

* [Enforce mBOM parts assigned to steps](/administration/production-settings/enforce-mbom-parts-assigned-to-steps)
* [Assign installation requirements](/build-hardware/procedures/installation-requirements-beta)
* [Manage BOM versions](/build-hardware/bills-of-materials/versions)