Direct Vent Fireplace Insert DV35IN33LN - Natural Gas Direct Vent Fireplace Minimum Fireplace Opening Requirements:. Height - 23 3/8". Front Width - 33 1/2". Rear Width - 22". Depth - 14 1/4" Insert REQUIRES a separately purchased surround for installation. Options: FQ-S353BL | FQ-356BL | FQ-SC356BL