I think this was a jet in a chamber with a slot all around it. I'm not so sure about THIS design but its tried and true. Take the Stryker wand for instance, a classic, tested 4 million strokes in china before it even touched the hands of everyday struggling bob and joe in the usa.
what ive noticed is manufacturers always really test the hell outta products so they dont just sell us a 10 pound bag of overpriced shit.