Use the Visualization tab page to assign custom parameters for the display of this element in 2D (plan) and 3D views. Parameters for the 2D symbol are on the left; parameters for the 3D view are on the right.
Typically, you will use these controls if you want to override the MEP System attributes assigned to this element.
If you adjust the material used in 3D views or renderings, you can still return to the System material settings: check the Use System Surface box.