The Master Flow 12 in. x 4 in. x 6 in. End Register Vent Boot has a maximum temperature rating of 360° Fahrenheit. It is made of 30-Gauge, galvanized steel to provide strength and durability. This HVAC part can be installed with sheet-metal screws. After installation, the seams should be sealed with code-approved mastic, sealant or duct tape.