Bobe Fire and Water 18" Smooth Flow Stainless Scuppers are made to withstand the elements, with no plastic used in their design. For a placid, smooth flow, internal baffles produce clear, bubble free cascading water at a rate of 25-30 gpm. The unique smooth flow design also prevents clogging, sagging, and warping. Female threaded inlet in back of scupper is standard 1.5" This elegant scupper is a beautiful complement to a custom made spa spillway. Appears flush with surrounding wall for pleasant aesthetic.