# External filter

{% columns %}
{% column %}

<figure><img src="https://4216107837-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FeYTtd7c0A325muFr5lMW%2Fuploads%2FK88npYZcpTw9Pr6L3Aq2%2Fimage.png?alt=media&#x26;token=c3ef33e9-a2e1-40bc-9e83-0d39a0ddd18b" alt=""><figcaption><p>External filter</p></figcaption></figure>

<a href="mailto:sales@sbtinstruments.com" class="button primary" data-icon="envelope">Contact SBT to purchase</a>
{% endcolumn %}

{% column %}
:label: Individual item number `50121`

:label: Bundled as `PF01`

&#x20;:straight\_ruler: Pore size **40 µm**

{% hint style="info" %}
**Not sold individually**
{% endhint %}
{% endcolumn %}
{% endcolumns %}

<table><thead><tr><th width="100">Item no.</th><th width="106" data-type="number">Quantity</th><th>Note</th></tr></thead><tbody><tr><td><code>PF01</code></td><td>2</td><td></td></tr><tr><td>Third party</td><td>null</td><td><mark style="color:$danger;background-color:$danger;">Not recommended</mark></td></tr></tbody></table>

## Use cases

Always have an external filter between your [BactoBox®](https://help.sbtinstruments.com/encyclopedia/item-register/bactobox-r) and the [tubing kit](https://help.sbtinstruments.com/encyclopedia/item-register/accessories/tubing-kit).

Replace the [external filter](https://help.sbtinstruments.com/encyclopedia/item-register/consumables/external-filter) in these cases:

* When you replace the flow cell.

See [install-tubing-kit](https://help.sbtinstruments.com/getting-started/installation/install-tubing-kit "mention") for instructions on how to replace the external filter

{% hint style="success" %}

### Replace the external filter when you replace the flow cell <a href="#replace-the-external-filter" id="replace-the-external-filter"></a>

It is good practice to replace the [external filter](https://help.sbtinstruments.com/encyclopedia/item-register/consumables/external-filter) whenever you replace the flow cell. See [Install tubing kit](https://help.sbtinstruments.com/getting-started/installation/install-tubing-kit) for details.

[run-qc-test](https://help.sbtinstruments.com/getting-started/qc-test/run-qc-test "mention") **when you replace the external filter.**
{% endhint %}

## Gallery

<figure><img src="https://4216107837-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FeYTtd7c0A325muFr5lMW%2Fuploads%2F1ITOJn9m0VFJfiN5hKRg%2Fimage.png?alt=media&#x26;token=532e2aa7-0730-46e1-afb5-9e7345054323" alt="" width="270"><figcaption><p>Two external filters bundled as <code>PF01</code></p></figcaption></figure>


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