Some air amplifier producers keep touting the use of plastic shims to maintain the small gaps necessary for the products to function. Ever look at thin plastic after a month of being subjected to a constant flow of never completely dirt free air, no matter how hard you try? It is not a pretty site! That is of course, if it hasn't worn to pieces. Min Shang distributed products only uses stainless steel shims - that lasts in the difficult environments these products are often subjected to. And we are typically STILL lower in price than similar competitive products using plastic. All of our vortex tubes are stainless steel with brass generators and high temp. O-rings - since the reason you use these products is to "cool". That means they typically are subjected to high temperature environments. Min Shang uses proper metal where possible to account for these realities - brass generators and stainless steel bodies for all vortex tubes.