primary fasteners 19a securely hold the fitting 10 against the main or main duct 20 as best seen in fig2 b the flange ring member 12 is disposed in substantially tangential relationship to the main 20 at opposed points on opposite sides of the flange ring member 12 the two fasteners 19a extend through the main 20 ring member 15 fabric ring member 14 fabric ring member 13 flange ring member 12 and base flange 11a and hold these elements in touching face to face relationship as best seen in fig1 b a sealing gasket or adhesive 22 is located between flange 12 and base flange 11a similarly a gasket or adhesive 22 is disposed between the flange 15 and the main 20 to prevent air leakage the entry portion of the cone 11 at flange 11a is larger than the exit portion of cone 11 near raised ridge 17 to allow for air flow 23 to more uniformly enter the fitting 10 relying more on air static pressure than velocity pressure the air flow 24 is balanced by damper 16 to provide a proper flow rate indicated by the arrow 25 entering the branch duct 21 a bracket 27 may connect the fitting 10 to the.