# SKU lists

SKU lists are used to group more [SKUs](https://docs.commercelayer.io/core-api-reference/skus), either automatically (i.e. through a RegEx — max **5000** chars allowed) or manually (i.e. by creating and sorting more [SKU list items](https://docs.commercelayer.io/core-api-reference/sku_list_items)).

{% hint style="info" %}
SKU lists cannot contain [bundles](https://docs.commercelayer.io/core-api-reference/bundles). If a bundle is associated with an SKU list, they are considered matching resources, which is meaningful for the scope of specific [promotions](https://docs.commercelayer.io/core-api-reference/free_gift_promotions) and [promotion rules](https://docs.commercelayer.io/core-api-reference/promotion_rules) application.
{% endhint %}

{% hint style="warning" %}
SKU uniqueness is not enforced on SKU list. That means an SKU list can contain the same SKU multiple times.
{% endhint %}

<details>

<summary>Data model</summary>

Check the related [ER diagram](https://commercelayer.io/docs/data-model/sku-lists) and explore the flowchart that illustrates how the SKU list resource relates to the other API entities.

</details>