They're simply 12V solenoids with an air valve attached, to that I've run a small 1/8th" tube to a piece of thin copper tubing that's open on one end. Nothing fancy or branded, the air valves are all attached to a manifold that divides the pressure from the compressor across all the valves.
12V on the valve -> air streams out of the corresponding tube.
12V on the valve -> air streams out of the corresponding tube.