Yes. Screw the adapter into the tank. Screw the air cylinder on to the adapter. Turn the big black knob to fill the cylinder. Use the air gauge on the air cylinder to monitor pressure. When you get to max pressure close off the air with the big black knob. Unscrew the air cylinder. Fill the air cylinder slowly so you don’t build up too much heat (which can turn into condensation in your air cylinder). Since it is a scuba tank that has 3000psi or less in it you won’t over fill the air cylinder. That said play it cool your first fill or two until you figure out how much air is left in the tank. I can’t remember the max air pressure for a FWB air cylinder. Walther is 300 bar (over 4000psi) so no way a 3000 psi scuba tank would over fill a Walther cylinder. Assume for now your FWB has a max fill of 200 bar (around 3000psi.) to be safe. verify the max fill pressure in the manual or look at the gauge on the air cylinder and see what it shows for max Psi. Hope that made sense and helped.
you can leave the fill adapter on the scuba tank. Just cover it with a plastic bag or something so dust doesn’t get into it Between fills.
