Our High Capacity Roof Caps Are Designed For High Performance Best Blower Systems, Handling Up To 1200 Cfm Airflow. Roof Cap Is Made Of 24 Gauge Crcq Steel Construction With A Black Primer Finish For Durability And Long Life. (Ul)(Li)High-Capacity Design - Up To 1200 Cfm(/Li)(Li)Built-In Spring-Loaded Backdraft Damper And Bird Screen(/Li)(Li)Not Recommended For Installation On A Flat Roof(/Li)(/Ul)