These are excellent quality back draft dampers;They are made from heavy-gauge galvanized steel with heavy duty springs;They use both an embossed bead and rubber gasket to help keep ducting securely in place;They prevent back draft air when your fans are off

• Ideal-Air 736988 Back Draft Damper, 12
• 12 Inch
• 12.3

Ideal-Air 736988 Back Draft Damper, 12iPower Distributor L&G