Models
Aluminum
51C - Grille Only
51C-O - with Steel Opposed Blade Damper
51C-OA - with Aluminum Opposed Blade Damper
51CD - with Rear Deflection Blades
51CD-O - with Rear Deflection Blades • with Steel Opposed Blade Damper
51CD-OA - with Rear Deflection Blades • with Aluminum Opposed Blade Damper
Steel
61C - Grille Only
61C-O - with Steel Opposed Blade Damper
61CD - with Rear Deflection Blades
61CD-O - with Rear Deflection Blades • with Steel Opposed Blade Damper