The exterior frame,lens and sill are one piece and cannot be separated. The port mounts from the outside the cabin and is held in place with sealant. Then the inside mouldings screw into the sill created by the outside frame. Replacement is necessary because the frames have become brittle and cracked. The ports are already out and I plan on using them as a template for new plexiglass to mount to the exterior. The problem is there is no sill or interior moulding this way and the hole is jagged and rough.