Round duct end cap closes off unused portions of round duct. Use with duct tape to terminate old ductwork runs in flexible duct or round metal duct. Sheet metal will come in 30 gauge or better. If you need a specific gauge, please call to place your order. Sheet metal is designed for rough in ductwork and is not made for applications where aesthetic standards are required. Inside may have duct sealant that is not applied by a machine and may look messy. The main function of the sealant is to seal air. Special Shipping note: Ductwork takes up a lot of space and some of it doesn't stack easily so larger orders will be packed into several boxes. Shipping will be charged accordingly.