FDIT CO2 Cylinder Refill Station Filling Charging Adapter Tool (G1/2(CGA320) 24")

This does work. I thought I was buying the one with a stainless steel tube. This tube is a real pain to use. The plastic is stiff and looped, so the smaller tank goes flying all over the place. The one with the stainless steel tube is also ~$10 cheaper.

The knob came off during the first use.

will not work to fill paintball tanks

They used keyword spam to mark this as being for paintball tanks. It is not. The threads are what you would find on SodaStream cylinders. Had to return it and now I need to find a proper adapter.