The unique design of the Flow Max offers 70% more drainage area than other scuppers. The angled ball slot allows full flow drainage, while the sure sealing ball is ground extra smooth to reduce leakage. Flow Max snaps securely into twist locks and easily twists off to clean. Scupper base is 3" in diameter and fits up to a 1 1/4" diameter drain hole. Meets ABYC specs for scupper diameter.