This 8" x 8" HVAC ceiling register box provides a durable transition between round supply ductwork and a square ceiling register or grille. Fabricated from 26-gauge galvanized steel, it features a nominal 6" round collar for connection to compatible round ductwork.The integral plaster-ground flange supports a secure, finished ceiling installation and provides an anchor point for register screws. This ceiling box is suitable for residential and commercial HVAC supply-air systems requiring an 8" x 8" register opening and a 6" round duct connection.Sizing Note: The first two dimensions identify the square register-box opening. The final dimension identifies the nominal round collar diameter.