Cap Holes used to make the wheel appear solid
Assigns the same smoothing group number to all new faces. If possible, this will be a smoothing group number not used elsewhere in the object.
Smoothes new triangular faces using the smoothing groups from bordering old faces. This smoothes only one level in from the perimeter of the border of the hole, so you might need to use both this and the Smooth New Faces option to properly smooth a large hole.
Makes all of the edges visible in the new faces.