ICP Weathershield Solid Pack Metal Chimney Caps

Measure the inside pipe diameter to determine your correct size.
The 6" - 8" round caps have an outside collar diameter of 12 1/2"
The 9" - 11" round caps have an outside collar diameter of 15 5/8".
The 12" -14" round caps have an outside collar diameter of 19".
This outside collar is what pushes down onto the top of the outer chimney pipe as you are sliding the inside collar (bottom of the chimney cap and matches the inside diameter of your chimney) and squeezes into the inner pipe of the chimney while pushing it down into the pipe.