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# preferredThicknessFraction

The preferred thickness of the split view item relative to the split view.

```
var preferredThicknessFraction: CGFloat { get set }
```

## Discussion

This value represents the proportion of the split view that you want the split view item to occupy on a scale of `0.0` to `1.0`. The system uses this value to adjust the thickness of the item in relation to other items when a user double-clicks a neighboring divider, and when the app enters full-screen mode.

The default value of this property is [`unspecifiedDimension`](/documentation/AppKit/NSSplitViewItem/unspecifiedDimension), which means the item doesn’t resize when a user double-clicks the divider, and the system preserves the absolute size when the app enters full-screen mode.

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