Wonder why your files seem to be blunt? They’re probably just clogged, the fine cutting surface of metal files easily choke up with particles, especially if you are filing soft non-ferrous metals as well as steel with the same file you naughty boy (we’ve all done it, who has two sets of files?!).
This fine pitch brush is designed for cleaning them up and a few strokes across the cut will get your files cutting efficiently again. Much cheaper than buying new ones!