430 has iron in it, 304 and other 300 series do not. Magnet sticks well to 430. The outside barrels and cabinets of RT are 430. Cheaper to use, and resistant to rust under ordinary circumstances. In salt air climates on the coast, the 430 will rust but not as much as steel. Also depends on quality of 430. I had another 430 SS smoker recently that was made of poor quality 430 and it showed rust from exposure to heat, and mild friction (where parts were bolted together). I have never had rust to my RT grills here in Oklahoma. Also, you can determine if metal is 300 series or 400 series with a magnet. Magnets won't stick to 300 series but do so to 400 series because of the iron. The "stainless" part of 430 is the coating. And it is the thickness of that coating that prevents rust. My magnets are Neodynium and really adhere to the 430. Please note, that you cannot stick them in areas that get hot, as they will loose strength while the grill is on. The control shelf/module is a good place on the 590, 700, etc series. But on the 1070, they work well on the cabinet walls away from the barrel.