Perko Adjustable Thru-Hull ScupperMade 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 4-3/4". The female portion of the scupper can be trimmed down by one rib for each 1/4" difference between hull thickness and 4-3/4". Specifications: I.D. inches: 1-11/32; O.D. Flange: 2-15/16"; Mounting hole diameter: 1-13/16";