they make 2 kinds of gauges
1. single- how much pressure is in the take
2. dual- same as above, but with a regulator & gauge so you can reduce the pressure coming out. (I use this one)
Go to your local gas/welding company should fill it less then $10.00
You will also need a coupler on the gauges to hook-up your airbrush to it.
If you need anything else just let me know.