The bottle should also be stamped with a bunch of numbers. 1800psi should be the max pressure. You could fill it with air to 1800, but I don't think that adapter on the end is a regulator so you would have the entire 1800psi at the output (Unregulated not like the co2). With other guns I run on HPA I have taken the co2 valve out of these bottles and installed a paintball regulator. You only get half the number of shots as a 13ci 3K bottle but it will work. I also take the 3K burst disc out of the co2 valve and use it in the PB reg so that should someone attempt to over fill it (thinking it was a 3K bottle), the disc will burst.