All you have to do to achieve that seal is to place this collar between the vent pipe and the roof flashing. It keeps moisture from seeping in from rain and weather, it's perfectly compatible with other DuraPlus venting components with a 6 or 8 inch inner diameter, and it carries a limited lifetime warranty. The weather protection your vent system needs is as easy as applying this easy-to-install DuraPlus All-Fuel Chimney Storm Collar.
I would recommend this item to a friend.
Chimney Storm Collar
April 9, 2012
Worked Great, easy to install.
Cons:Used a rivet to lock collar together instead to bending the lock tab over.