20 express hardtop antenna/mast question

We were going over the boat lastnight, taking pictures, establishing a list of materials that we will need. Does anyone have any info what apears to light/antenna mast that goes on the hard top? I also am trying to find any info on the cabin setup.

I forgot, duh might need a picture of what the wide world of sports I was talking about. Its kind of hard but the circled area is what I am trying to describe.

[FINS]

Just a guess, but looks like the plug in base for a mast light. Does the base have wiring, possibly to a switch? The pole and light portion are available in different lengths that most likely will fit the same base.