3 Hour Out Of Air Fire Door Grille 2663-36X22 Step Down Ceiling Diffuser Spiral pipe diameter must be

Spiral pipe diameter must be 4” larger than Height of the duct opening

Negator stainless steel closure springs mounted on spring pin brackets

904 - Double Deflection Adjustable Aluminum Blade Grille For a 24" x 8" Duct Opening   (front blades parallel to shortest dimension)

22 gauge butterfly style galvanized steel blades

3 Hour Out Of Air Fire Door Grille 2663-36X22 Step Down Ceiling Diffuser Spiral pipe diameter must beh3. Standard Features * 2661 Square or rectangular fire door for vertical mount only. Maximum dimension 60x60. For damper free area chart A click here * 2663 Out of Airstream fire door. Square or rectangular for vertical mount only. Maximum dimension 60w x 52h. For damper free area chart B click here * 2665 Round fire door for vertical mount only. Available 4" thru 52" round. * 3 hour rated * UL and California State Fire Marshall approved * 4 1 4"