As a bench jeweler I can give my advice about this product, is that is not necessary to own, of course it's a really good product really nice and very well made, but very expensive and it won't last long especially if you use it on hard material such as 14K 18K white gold for example.
If you have needle or machinist files, the best way is to stick a little piece of 3M adhesive imperial film and you'll have the same product, it's even more interesting as you can have several grit.
I've simply wrapped various fine grades of emery around a toolmakers file and it works just fine. I suppose if you're working strictly on gold and silver these tool may have an advantage, but emery wrapped around a file works very well.
Lots of good tips here. Thanks Mitch. I just bought 4 of them. I prefer the files for my work because the never round the fine cuts. I will look for the fine adhesive paper