Probably factory, so the factory front sight is the lowest of the 3.
This could cause an issue , in that the 14 inch barrel mossberg have a tendency to shoot high and now if you put a ghost ring sight on a rail you might not be able to lower it enough to bring down the point of impact.
Remember, the rear sight is your friend, it goes where you want , want to shoot high , raise it , want to shoot left , move it left.
If you're sticking with the rail, a red dot would be the best option.
Or something like a UTG Sub compact rear sight might work.