The Size Delta Sizer can change the width and / or height of a Rect Transform according to the resolution.

The Settings section is a Size Config Collection defining for each Screen Configuration if it should Apply the Width or Height (or both or none).

The Size Delta Settings section is a Size Modifier which defines the Width (X-Value) and Height (Y-Value) which is applied to the rect transform.

Note that both settings are used in combination. So, if "Apply Width" is checked but "Apply Height" is not, the X-Value of the Size Delta Settings is used while the Y-Setting is ignored.

Also, note that the Size Delta Sizer may have an unexpected behavior if the anchors of the Rect Transform are not at the same location. If you need more control over the Rect Transform, use Better Locator instead.