316 Stainless Steel. On the exterior, they have a smooth edge over the competition. There is no protruding cap to cause damage- or be damaged by- hull bumps or scrapes. Cap unscrews with hex head wrench for easy cleaning of filter and pressure testing of entire fuel system. Includes two silicone gaskets. 2-year warranty. Type Straight Hose 5/8" I.D. Max Hull 7/8" Hole 1-3/8"