Miami Tech R4MTB120808 - R4 Metal Top Register Box With Collar, 28 Gauge, 12' X 8' X 8'Product Description 1' perimeter flange provided for easy installation. Design includes 1/2' drywall lip and rounded corners for added safety. Opening 1/4' oversized to accommodate register/grille. Dual Bead design for added strength. Black diffuser board coated with EPA registered anti-microbial protective acrylic agent along air stream side. Collar installed with expansion lock and then sealed air tight with hot melt glue.