CO2 Cylinder Refill Adapter for CGA320 CO2 Tank to Refill TR21-4 CO2 Canister, CO2 Refill Station Connector Kit Compatible with FIZZI ONE TOUCH JET Soda Maker

Excellent. Worked perfectly for refilling the small bottles from the larger 20lbs. bottles. A great deal.

I ordered this $16 Gurudar CGA320 TR214 adapter (Amazon ASIN B0DQKY8NKY) so that I could more easily refill my 14-1/2 ounce (425g) soda-machine DOT-SP 20796 (older designation DOT-SP 15634) carbon dioxide canisters with liquid carbon dioxide. This inexpensive adapter is simpler to use than the stainless steel braided hoses I was using prior to refill the soda canisters. Note that this valve pays for itself in your first exchange of two canisters, so it's a no-brainer for anyone who already owns a larger carbon dioxide tank.My larger carbon dioxide tank is a five pounder which I fill myself using dry ice from the local grocery store, but this valve works with any US carbon dioxide tank that has a CGA320 valve on it. The important threads are those on the output of the CGA320 valve which is attached to the CO2 tank. Those threads that normally connect to a regulator are male "0.825-14 NGO RH" outlet threads.The specifications for the male CGA320 outlet threads are: Nominal Diameter: Approximately 0.825 inches Threads Per Inch: 14 Thread Type: Right-Hand, Non-Gas Outlet (NGO) with a flat nipple.The soda canister valve that fits this adapter are those older (blue) ones with TR21-4 threads.The specifications for the male TR21-4 threads are: TR: Indicates a Trapezoidal thread type. 21: Indicates a nominal diameter of approximately 21 mm. 4: Indicates a pitch of 4 threads per inch.The adapter contains the female threads to match both those male threads above.  To refill your soda canister, you first have to determine what type of carbon dioxide tank you have. Mine does not have a siphon valve, so mine has the liquid on the bottom and the gas comes out on top. Those with a siphon valve allow liquid to come out the top so you don't need to invert those with the siphon valve. But mine I have to invert to allow the carbon dioxide liquid to fill the soda canister by pressure & gravity.The amount of carbon dioxide it takes to fill the soda canisters from empty to full is about 425 grams or about 14-1/2 ounces by weight of carbon dioxide liquid. If I start with a five pound carbon dioxide tank, I can fill about 5-1/2 canisters, but there are losses to sublimation so I generally garner about 5 canisters per five pounds of carbon dioxide.Instructions are provided which I've taken the liberty of posting in this review so that those who have never refilled a soda canister can see what the filling & troubleshooting steps are. It's easy if you're handy. But if you are not handy, I wouldn't recommend trying this though, as a full carbon dioxide tank will be pressurized at around 800-900 psi at typical room temperatures (around 70°F or 21°C) although higher temperatures can push the pressure well above 1000 psi (gauge pressure).Overall, this is a nice small convenient cost-effective well made solid brass adapter for connecting a donor CGA320-valved carbon dioxide tank to a TR21-4 valved soda canister for convenient home refilling. For more information, please see the included detailed photos. In explaining all of this, I hope you appreciate if this review helps you make a more informed decision.