Pro Quip Fast Pour Plastic Fuel Cans use a nitrile “C” seal on the pourer which is utilised in both pouring and storing. The seal is correctly positioned when it is wrapped around the flange of the pourer. This allows it to press against the neck of the fuel can as well as both the stopper disc when stored, and the underside of the screw cap when positioned for pouring. If the seal is dislodged or has suffered damage, it will not effectively seal the can allowing vapour to escape through the cap. The vapour will pool in the thread of the cap and dribble down the front of the can, pooling beneath it. We therefor recommend always inspecting the seal on each use to make sure it is seated correctly and in good condition.