Crystal Fires Super Heatrave Inset Gas Fire ( Natural gas only ) The Super Heatrave radiant inset gas fire from Crystal Fires has been a popular choice for many years due to its impressive 3.9kW Heat Output (6.5kW Input).Efficiency: 60%Full depth fuel bedSuitable for Class 1 and Class 2 Flues subject to a minimum depth requirement of 175mmOpen-fronted gas fire Control Type: Remote Control Fuel Type: Coal Dimensions: Height 600mm X Width 460mm X Depth 180mm