Effectively terminate a rectangular duct run with this Imperial Rectangular Duct End Cap. The 3" x 10" duct cap is used to block off the main trunk duct within an HVAC system. Built to last, this blind end cap is constructed from 30-gauge galvanized steel for rust resistance and durability. The end cap is easy to install with sheet metal screws for a secure fit (screws sold separately). It is suitable for use in most heating, venting and air conditioning applications.