The gauge I referenced attaches to the threads on the propane tank, then the appliance attaches to the gauge. It is never removed from the system. Common for use on propane grills, etc. Like I mentioned, I used one for many years with my truck camper. It is only accurate when you are flowing propane, if you want to get an idea as to volume remaining. A propane fridge alone does NOT flow enough vapor to let it read accurately. To get a remaining volume reading, check it when you have a stove burner or 2 going - fairly accurate then. Very good for checking leaks in the system like I outlined previously. ST