Perko Adjustable Thru-Hull Scupper Made from molded white polymer, this adjustable thru-hull scupper from Perko is exactly what you need for your boat! It has a recessed soft black flipper to prevent back wash, and is designed for surface thickness between 2 and 4-34. The female portion of the scupper can be trimmed down by one rib for each 14 difference between hull thickness and 4-34. Specifications I.D. inches 1-1132 O.D. Flange 2-1516 Mounting hole diameter 1-1316 California Residents WARNIN