Regency Greenfire GFI55 Medium Pellet Insert Heats up to: 1,500 square feet 45,000 Max BTU Burn Time: Up to 36 hrs View Area: 161 sq. in Qualifies for 30% BioMass Tax Credit. Including Installation! Regency's Greenfire Medium Pellet Insert includes an adjustable hopper, allowing this unit to fit into fireplace openings as low as 19.5"....