> For the complete documentation index, see [llms.txt](https://frinn.gitbook.io/custom-machinery-1.19/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://frinn.gitbook.io/custom-machinery-1.19/creating-custom-machines/machine-components/item-component/upgrade.md).

# Upgrade

The item component variant that hold upgrades.

Use this variant to make an upgrade slot.

The slot will be able to hold [Machine upgrades](/custom-machinery-1.19/recipes/upgrades.md) and apply them to recipes.

{% hint style="warning" %}
The ["mode"](/custom-machinery-1.19/creating-custom-machines/machine-components/item-component.md#name-mode) property of an item component with fuel variant must be `"input"` or `"both"` to let the player place upgrade items inside the slot.
{% endhint %}

### ID

```json
"variant": "custommachinery:upgrade"
```

### Accepted items

Any item that are defined as machine upgrade and match the filter defined in the item component ["filter"](/custom-machinery-1.19/creating-custom-machines/machine-components/item-component.md#name-filter) property.

### Example

A simple upgrade slot : 

```json
{
    "type": "custommachinery:item",
    "id": "upgrade",
    "mode": "input",
    "variant": "custommachinery:upgrade"
}
```