I use this to easily transfer propane from my grill tanks to my camping tanks. The gauge is accurate, as far as I can tell, and the build quality feels substantial. I haven't noticed any leakage or anything to make me think it doesn't function properly. Easy to use, and will save you considerable amounts of money if you go through propane tanks.

Nothing like picking up your camping/soldering propane tank just to find it nearly empty. I use these tanks for my camp grill, my blow torch (easiest campfire starter ever), and my soldering torch for plumbing. With this handy refill adapter, I can hook up to my home grill's propane tank and fill up these little containers more easily.

Hook up each end, make sure the red handle is off, turn on the gas on your big tank, open the red handle to fill your smaller tank, close the red handle, open the red handle again to push more in, close it again, repeating this process until the gauge shows the bottle is full, disconnect small bottle, attach your next small bottle, then repeat opening and closing the red handle to fill the next bottle. Once done, turn off the gas on the big tank, remove the small tank, and open the red handle to expel the gas trapped in the line. Super easy to use.

Now using a refill kit like this can be dangerous so think about what you are doing at each step and don't get distracted. Wear gloves and eye protection.

That being said, you can really save money over buying those little green tanks in the store. Here is as tip: if you want to get more propane in your little tank, put them in the freezer first to cool them down before you fill them. Second tip: refill your large tank from a friend's large home propane tank rather than exchange it at one of those places like you see at Walmart or Home Depot or wherever. They don't fully fill those exchange tanks and you are paying double the price your friend pays per gallon. Note: your friend has to have a wet leg on his big tank to fill yours. A lot do have them.

There is no difference in that propane than what you buy at Walmart if they have a reputable supplier.

Now you can do this at home and do it for friends but there are laws prohibiting refilled tanks from being transported across state lines. Now you know.

One last thought, the gauge that is mounted on the hose is for general reference. It can vary with temperature. But when it says your empty, you are.

This comes in a clear plastic bag with no directions. So you need to know what you are doing. It is recommended to have the main tank be under 42° so that you are filling liquid and not gas fumes. It works, saving us money and being more green.

I very much like this design it’s easier to work with with the length of the hose that comes with this adapter. I like it so much it actually replaced my old adapter.
I have found out for maximum capacity put your empty propane bottle in the freezer for at least 30 minutes, connect the adapter and then purge for a second to get the air out of the line.