Optional Flue Extension For B58 Range Hoods In Stainless Steel Optional Flue Extension (27-3/4" Long) In Stainless For Use With Select Broan? Range Hood Series. Flue Extension Can Be Used In Ducted Or Non-Ducted Applicatons To Suit Your Needs. The Optional Flue Extension Accomodates 9' To 10' Ceiling Heights