Anti-Downdraught Cowl Manufactured To Fit A Single Skin Rigid Flue Pipe And To Reduce Downdraught. Anti-Downdraught Cowl Designed To Fit Over The End Of A Single Wall Rigid Flue Pipe. Designed To Fit Over The End Of The Pipe And To Be Drilled And Screwed On,Approx 5mm oversized base.