Attwood Marine Scupper Valve Provides a water exit for boats with self-bailing cockpits. Acetal construction. Accommodates 3875B thru-transom thru-hull connector (screw holes must be drilled for installation.) Diameter: 2-7/8. Use as a replacement valve for 3881 Thru-Transom Scupper. Caution: Thru-Hull connectors are designed for installation above the water line only.