Vented loops are vital components to reduce the risk of sinking or flooding. The glass reinforced composite Marelon™ Vented Loops allow air to enter the lines preventing that dangerous back siphoning effect. Use above the waterline on your head discharge system, bilge pump, the engine, gen-sets, air conditioners, ballast tanks or other equipment. Vented loops help make sure your boat stays afloat after the pumps are turned off. Model MF842 Hose 3/4" Barb Size 3-3/4" W x 4-1/2" H