Extra corrosion resistance for Mercury fuel filters installed in harsh environments For 50 years Sierra has been producing parts engineered to meet or exceed the specifications of marine engine manufacturers and has gained the confidence of engine manufacturers and boat builders to a point of supplying them with OEM parts. Boaters can be assured a Sierra part will fit and restore function. This Filter head is an example of Sierra improving on an OEM part. The stainless steel construction provides added corrosion and fuel resistance compared to coated aluminum heads that were originally installed. Matching bolt hole pattern makes installation easy. Included are two brass plugs to seal unused ports.