The difference is in the hole in the blade....the notched holes will not fit Martelli cutters. The round holes will, as well as Fiskar's. HF has a round hole so if you are trying to use it in an Olfa cutter, it will not perform.[/quote]
I have a martelli cutter and they fit fine I have no problem with mine I do clean them well before I put them in my cutter....
they fit the olfa I have too....