If you are replacing an original HF72 or HF73 flush mount Helmsman compass with one of the newer HF742 or HF743 Helmsman models...
If you are replacing an original SS-1000 flush mount SuperSport compass with the newer SS-1002 model...
You will need to purchase an H-ABLK or H-AWHT adapter ring.
The adapter compensates for the smaller size of the newer compasses, so they don't fall into the original mounting hole.
Each adapter comes with a mounting gasket and fasteners.
See Related Products, below.