ATTWOOD 316 stainless steel alloy flush-mount fuel vents provide a highly polished, low-profile exterior to minimize damage and snags on boat hulls. The flush cap is slotted for a separate key, sealed with an O-ring for watertight protection, and is attached by a stainless steel beaded chain; the cap unscrews with a hex head wrench for easy access to the filter and pressure testing of the fuel system. Each unit includes two silicone gaskets and features a 3-1/4" fill neck that fits 5/8" I.D. hose. Models in this product family cover common installation preferences and deck-fill needs; specific installation hole sizes and maximum hull thickness vary by model.