HBW floor register is made of heavy duty steel and powder coated in brown. It has built-in damper to control air flow. There are two screw holes on each side of the register to fix on the surface of floor, wall or ceiling. Floor Register Measurement Outside overall dimension is 13.25” in length and 7.25” in width Duct opening – a hole that holds the duct neck to allow air to come out from HVAC system. This register fits in a duct opening of 12” in length and 6” in width. Size Selection Guide Measure the size of the air duct opening(the size of the “hole” ) . Measure the duct opening Match the duct opening size with the listed size of 12” x 6”.