On this tab of the properties dialog box, you can modify the plate size and the material.
Width X
Defines the plate width in X direction.
Length Y
Defines the plate length in Y direction.
Convert to polygon
If checked, the selected rectangular plates are converted into polygon plates. Plate features are not considered.
Note: Polygonal plates cannot be converted back to rectangular plates.
Thickness
Allows selecting the plate thickness from the drop-down list as well as entering a custom value.
Material
Lists all available materials for the plate.
Coating
Lists all available plate coatings.