These Fantech Silencers are perfect for reducing sound levels without interrupting ventilation. The silencers are made out of galvanized steel and come in 4", 5", 6", 8", 10" and 12-3/8" ducting sizes. The silencers reduce system sound levels by over 50%. The silencers feature a rubber seal on the inlet and outlet to insure a leak-free seal. These items ship via UPS or FedEx.