Propane has a meter that tells you how much pressure you're rotating the knot to release the gas, allowing you to adjust your fire better and make your stove/grill/buner/smoker/Turkey fryer look like new. The red knob can be regulated the gas flow and pressure.( Adjustable pressure range: 0-30PSI ) Equipped with Excess Flow Protection. When your propane gas left in your tank too low, or the capacity flow of your appliance exceeds this regulator's Max. It will shutoff the gas flow automatically.