If you use a SCUBA tank that adapter screws right onto the valve. If you look into the SCUBA valve where the air comes out it looks like it will accpet a big allen wrench, that's because it does. Use and allen wrench, and the moddle of the valve screws out (no need to remove air, this is not pressurized when the valve is closed). Uncrew that big allen screw and screw your adapter into the hole. Fill the tank as you normally would using the gauge on the air tube to monitor your fill, fill slow. That's it, no adapters needed, just the thing you already have and your gun. If you fill from a pump with a Foster end, then you need the adapter like was mentioned above. Hope this helps,