This AP Products Complete Automatic Changeover Propane Regulator Assembly automatically switches to reserve cylinder when primary empties. Specifications•Inlet Size: 1/4 Inch•Inlet Attachment Type: Female Threads•Outlet Size: 3/8 Inch•Outlet Attachment Type: Female Threads•Installation Type: Vertical•Number Of Stages: 2•BTU Level: 225000 BTU Per Hour 1 Stage/ 150000 BTU Per Hour 2 Stage•Material: Cast Zinc•With Hose: Yes•RV Approved: Yes Large Flow Indicator Knob Designates Which Cylinder Is Primary Red & Green Pressure Indicator Float Indicates When Cylinder Is Empty Pressure Adjustable | AP Products Complete Automatic Changeover Propane Gas Regulator Assembly