If you plan to regularly fill to max pressure, you'd best get a compressor. Dive tanks can hold that high pressure, but after a couple fills of the gun, tank pressure will drop below max for the Avenger. My reg is set at 1800 psi and I only fill to 3600 psi so my dive tank lasts for quite a few fills. When shooting indoors in winter, I fill to over 4000psi so I use a Trailcharger compressor.