How to measure for Chimney Master Multi-Flue Chimney Caps. Just keep it simple and it's easy

The minimum base size is FAL (plus 1") X FAW (plus 1")
The maximum base size is L (minus 3") X W (minus 3")
Note: The lid size is 5" greater than the base size

Example: FAL= 32", FAW= 16"
L= 52", W= 24"
The minimum base size would be 33" x 17"
The maximum base size would be 49" X 21"
Note: Based on the above example any cap that falls between the minimum and maximum size ranges will work. The minimum will provide protection of the flues at the lowest cost. The maximum will give the most protection and achieve the most balanced look.

L Length of entire chimney
W Width of entire chimney
FAL Flue Area Length
FAW Flue Area Width

The screen height should be at least 5" higher than the tallest flue.