Reve Porter Cased Coil Boxes (CBX) are designed to fit under a standard-width furnace in downflow applications and hold an uncased evaporator coil. The box depth is 20 1/2” and the height is 28”. All downflow boxes are insulated with 1/2” fiberglass insulation. These boxes have a door panel screwed onto the front and a removable bottom panel inside the box.