Determining Vent Size

This has been a reoccuring question, and one that will be addressed on our website. Vents come basically in 1 1/2 inch, 2 inch, 3 inch, and a rare 4 inch. However, the flashing is about an inch wider than the diamter of the actual vent. So a 1 1/2 inch vent will have a
2 1/2 inch diamter lead flashing, a 2 inch vent will have a 3 inch flashing, a 3 inch vent a 4 inch flashing, and a 4 inch vent a 5 inch flashing.
So when you measure your vent, if your lead flashing diameter is 4 inches, this is a 3 inch vent and a Size B CQ would be needed. If you measure 3 or 2 1/2 inch flashing that would be a 2 or 1 1/2 inch vent and a Size A flashing. If you measure 5 or more inches thats a 4 inch vent, which we do not supply a shield for currently.
So dont be confused, remember. 4 inch flashing, Size B. Smaller flashing, Size A.