For use with Vented or Vented/Vent Free Slope Glaze Burners 36 in Minimum Firebox Size for Millivolt or Variable Remote Burners 42 in Minimum Firebox Size for Manual Burners Includes Burner amp Valve All burner choices are 38 000 Btus These burners are vent free systems that can convert to vented systems by opening flue damper NOTE VENT FREE APPLICATIONS ARE RATED FOR A MAXIMUM ELEVATION OF 3500 FEET - Buy Now or get More Info on Empire Fireplaces - Click Here To Order