While stainless steel gets a large part of its corrosion resistance from chromium, there are near-endless combinations of various metals marketed as stainless steel today.

So there aren’t any new features that’ll drastically improve the performance. Yes, the battery is a bit larger and there’s that 32bit MCU, but the latter doesn’t seem to make any difference whatsoever in terms of shaving performance. When you say de-natured, is this the same as grain alcohol? Or Isopropyl? The reason I was considering ethyl alcohol was because I’d read that certain other additives don’t dissolve when added to isopropyl, but apparently do so in ethyl alcohol. Not sure whether or not that’s correct.

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Series 9/9 Pro or the Series 8 if you need a very comfortable and versatile shaver that can also deal with longer stubble As for the Series 9, I don’t think it’s worth spending the extra money considering your husband’s shaving routine and facial hair. But if you still decide on getting one, it doesn’t really matter which one is it as long as the model name starts with 92 or 93. They all shave the same and you really won’t miss any of the extra features. Again, during actual use it will be slightly louder as the blades shear against the foils, cutting the hairs and making more noise. Cleaning and maintenance

Also, when I look closely at the showing head icon, it looks like there is only one LED behind the icon, meaning that the 3 tiny lines can only be shown at the same time and not individually. Many duplex grades offer a combination of properties from both austenitic and ferritic stainless steels. But the actual performance is the same as the rest of the cutting elements stayed exactly the same. If you want to buy a new razor, my suggestion would be to get a Series 5 from the generation that followed the 530S-4. I wrote a detailed guide about those models here.The new trimmer on the 94M does seem to be a tad better with longer hairs, but it would be really difficult to quantify the benefits; both the Pro S9 and the standard one seem to me just as capable with longer stubble. You won’t have a Series 9 Pro though after that upgrade as using a standard Series 9 with the 94M Pro head will pretty much feel like using a standard Series 9.