FORESPAR #903009. 1-1/8 VENTED LOOP. Keeps fluids from siphoning from tank to tank. Loops are commonly used in the marine toilet system and engine cooling system. The valve in the top of the loop allows air to enter the line when not in use and seals when water or other fluid passes through. Made of Forespar's glass-reinforced, non-corroding MARELON. Duckbill valve seals properly if paricles are present in fluid. 1-1/8.