Green Marine Fuel Whistle for 5/8 Fuel Lines This whistle is 3 3/4 in length, but once installed takes up a 2 X 2 space. To install this item you would cut the fuel vent line near the fuel tank. The whistle is inserted into the fuel vent line and held in with clamps (clamps not included). The whistle needs to be oriented within 45 degrees of vertical to allow for proper drainage should fuel pass through it. It has molded mounting ears so that you can secure it in place with 2 stainless steel screws. This product will help you protect the environment and avoid costly fines.