The popular 3876 scupper mounted to a 3875B 1 1/2" thru-hull as a complete assembly. Made of high-impact plastics with rubber flapper valve that opens outward to dump water overboard and closes to help prevent backwash. Hose ID is 1 1/2" overall length 6 1/4L" Max hull thickness 2 5/8" Overall diam 2 3/4" Installation hole is 2" White