The Master Flow 8 in. x 4 in. Insulated Duct board Register Box helps connect a round pipe or insulated flexible duct to an air register or grill. This duct board is pre-insulated with R6 fiberglass insulation. The insulation helps to absorb condensation and noise for a quiet and efficient system. This register box has a minimum temperature rating of 100 degree F and a maximum temperature rating of 390 degree F.

Made of zinc-coated， 30-Gauge galvanized steel

Designed to connect round pipe or insulated flexible duct to an air register or grill

Pre-insulated with 1 in. fiberglass insulation lining helps absorb HVAC system noise and control condensation

R6 insulating value results in higher thermal efficiency for duct board products

Features a minimum temperature rating of 100 degree Fahrenheit and a maximum temperature rating of 390 degree F

Always seal seams with code approved mastic or sealant (or duct tape)