Simplify
The simplify tool removes redundant regions, faces and edges.
Dielectric boundary faces are redundant if they have the same medium (for example, metal, free space, dielectric) on both sides. When a face separating an internal free space region from the outside free space is deleted, the internal region is merged with the outside. Since the outside medium is free space, faces can only be removed from closed regions if the internal medium is set to free space.
Edges are not redundant if the face normal on either side of the edge are in opposite directions.