Micro Air Control or simply MAC valves are a must in airbrushing. Okay not a must but one hell of a convenience. With them attached to the air hose, you turn every airbrush into an Iwata Hi-Line.
The way they work is not rocket science. You simply have a screw that opens or closes an air passage. But the quality of material and how well they do what they need to do, is what sets them apart. My first ones that I got were just cheap no-name brands from a UK shop. They worked for about a year. Then the coupling part started leaking but the valve were still fine. I replaced them with some more no-name ones off Ebay. They looks exactly the same but were no good at all. More about that in “Likes and Dislikes” below. They were then replaced with Sparmax ones. They worked great and is still going strong. But why stop there. Then I saw Harder and Steenbeck also makes some. So I ordered some from Everything Airbrush and that brought me to this shoot-out. There are still ones from Grex and Iwata but Everything Airbrush does not stock those and besides, the Iwata ones are not quick couplings.
Here are the weights of each unit. You think it does not matter but combined with the weight of the airbrush and the hose, it adds up. That is one of the reasons I use the thinner and lighter Iwata hoses.
Weight
No-name: 19g (0.67oz)
Sparmax: 20g (0.71oz)
Harder & Steenbeck: 17g (0.60oz)
Size
Here you can see the overall length of each of the units. Functioning parts are all about the same size. It’s the length of the threaded parts that are different.
Side-by-side view from the top.(L) is for Length.
No-name: 37mm (1.46″)
Sparmax: 38mm (1.50″)
Harder & Steenbeck: 32mm (1.26″)
When it comes to the width, there is no difference in the bodies. It’s only how far the dials protrude that are different. I measured it with the dials fully closed and fully opened.
Side-by-side view from the top. 
is for Width.
No-name: CLOSED: 18mm (0.71″) OPEN: 20mm (0.79″)
Sparmax: CLOSED: 16.5mm (0.65″) OPEN: 17.5mm (0.69″)
Harder & Steenbeck: CLOSED: 14mm (0.55″) OPEN: 16mm (0.63″)
Next I measured how much the hose fitting adds to the couplers. The hose is an Iwata One-shot hose. Due to different length threaded sections on the couplers the overall length is also affected.
Coupler attached to hose. (tl) is for Total Length.
No-name: 41mm (1.61″)
Sparmax: 40mm (1.57″)
Harder & Steenbeck: 35mm (1.38″)
Other notes that I made are how many turns it takes to open and close the air.
No-name: It has a 1½ turn dead spot before it starts to open then ½ turn to fully open. Continues turning a few more times until it locks.
Sparmax: ¾ turn and continues to turn but never locks.
Harder & Steenbeck: 1 turn but continues to turn a few more times until in locks.
On the subject of the dials. The Harder & Steenbeck’s one one small and really tucked up against the body. Big hands will find it difficult to adjust. It is also not serviceable like the other two.
LIKES and DISLIKES
No-name
Likes: Cheap(er); chrome finish; serviceable
Dislikes: Release sleeve scratchy; finish feels cheap; does not last long; dial has huge dead spot before air flows
Sparmax
Likes: Chrome finish; serviceable
Dislikes: Price almost as much as H&S but not the quality; finish on black dial starts coming off after a year’s use
Harder & Steenbeck
Likes: Weight; build quality
Dislikes: Nickel plated not chrome; price; small dial; not servicable
CONCLUSION
Without the dials, all three works fine as quick couplings. The opening on the H&S is a bit smaller than the others. I guess they want you to use their male coupler parts but other no-name and even Iwata male parts still fit it perfectly.
I still can’t make up my mind if the name and build quality of the H&S is worth the few extra bucks over the Sparmax. All I know the no-name brand is off the table, forever.
FINAL CONCLUSION (30 October 2016)
It’s been more than 2 months after the review and I can say the Harder & Steenbeck are indeed worth the extra money over the Sparmax one. The dial is just smoother and more gradual.
AVW AirbrushWorks 