Marine-Grade Construction: Solid cast 316 Stainless Steel for durability and resistance to corrosion. Back-Flow Prevention: Internal flapper design prevents water back-flow for enhanced functionality. Sleek Polished Flange: Highly polished flange elevates the boat's appearance for a stylish look Versatile Compatibility: 1-7/8" threads for transom passage, hose barbs fit 2" I.D marine hoses. Original Equipment Quality: Trusted and used in various offshore saltwater fishing boats for reliability. This 316 stainless steel thru-hull scupper is designed for marine applications requiring reliable drainage and back-flow prevention in high-moisture and saltwater conditions. Manufactured using precision casting techniques, the solid construction provides long-term resistance to corrosion, pitting, and mechanical degradation. An integrated internal flapper valve prevents water from re-entering through the fitting, reducing the need for bilge pump activation and helping to keep the bilge and transom areas dry. The flange surface is mirror-polished for reduced friction and improved sealing during installation. A 2-inch hose barb enables secure attachment to standard marine-grade hoses. This unit includes a threaded 316 stainless steel mounting nut for installation. Outside Flange Diameter: 3-5/8 inches Thread Length: 1-7/8 inches Overall Length (Inside Flange): 4-1/4 inches Required Hole Size: 2-3/8 inches Hose Inner Diameter (ID): 2 inches Flapper Diameter: 1-3/4 inches Material: Solid Cast 316 Stainless Steel Finish: Mirror-polished Valve Type: Internal flapper for back-flow prevention Mounting: Includes 316 stainless steel threaded nut The use of marine-grade 316 stainless steel ensures consistent performance in saltwater exposure, with enhanced resistance to chlorides and acidic contaminants. The integrated flapper valve minimizes reverse water flow when the vessel is stationary or underway in reverse, supporting dry bilge operation and reducing system load. The 2-inch hose barb offers compatibility with standard marine drainage systems, while the included stainless steel nut ensures secure threading without requiring additional hardware. This scupper is suited for OEM installation or aftermarket upgrades on offshore fishing boats, coastal cruisers, and performance watercraft. It meets durability, dimensional precision, and corrosion resistance requirements for demanding marine plumbing applications.