Skin fittings for over and under water-line. Made of fiberglass reinforced plastic. These thru hulls are the only ones made of plastic twith the IMCI certificate. Delivered including sealing washer. Specifications:Made of fiberglass reinforced nylon composite material Fits all types of hulls - aluminum, steel, wood and GRPResistant to corrosion and electrolysis Chemical-resistant (e.g. diesel, gasoline and antifouling)UV-resistantHigh quality surface coating Can be covered with all types of antifoulings