For use with Vented or Vented/Vent Free Slope Glaze Burners 36 in Minimum Firebox Size for Millivolt Burner 42 in Minimum Firebox Size for Manual Burner Includes Burner amp Valve All burner choices are 60 000/75 000 Btus These burners ship assembled at the higher Btu listed Lower Btu orifice is included - Buy Now or get More Info on Empire Fireplaces - Click Here To Order