Broan-NuTone 634M Roof Cap Black Up to 6" Round Duct Footprint is 18-3/4" long x 14-1/4" wide for a well-balanced fit Designed to fit 6" round duct A built-in, backdraft damper and bird screen provide a dependable roof cap you can count on Roof cap is made of 24 gauge CRCQ steel construction with a black electrically-bonded epoxy finish for durability and long life For use with Range Hoods, LoSone Fans and Bath Ventilation Fans