Hi Max,
I have the same one and it is a great compressor. 3 liter air tank and very quiet. The red cap with the ring in it on the tank is the over pressure relieve valve if the pressure should get (not likely) too high. After using it, you can pull up on the ring and empty the tank too. The other red ring by the gage is the base for the pressure control knob. When you pull the knob up , you can adjust the spray pressure for your airbrush. You got it for a fantastic price too!!! Have fun and enjoy it...
Prost
Allen
I have the same one and it is a great compressor. 3 liter air tank and very quiet. The red cap with the ring in it on the tank is the over pressure relieve valve if the pressure should get (not likely) too high. After using it, you can pull up on the ring and empty the tank too. The other red ring by the gage is the base for the pressure control knob. When you pull the knob up , you can adjust the spray pressure for your airbrush. You got it for a fantastic price too!!! Have fun and enjoy it...
Prost
Allen