Cannon Low Profile Swivel Base is corrosion-resistant because of the way it is created. The 316 stainless steel not only prevents corrosion but adds strength. This downrigger swivel base is square with holes on each corner. In the middle circle is another square indention with holes in each of those corners as well. It s all silver in color with a knob on one side. It features 16 locking points with a base that allows for 360 downrigger rotation with locking positions every 22.5 for added control. Do check the parts number to make sure this is the correct replacement. These downrigger accessories are sure to help the home mechanic as well as the professionals get the needed repairs taken care of.