I had given up using my Martelli cutter after cracking 2 blades in it then I saw something that explained the notches on the Olfa blades. The Martelli cutter doesn't have a tension spring like the Olfa cutters do so it wobbles if you use the notched blades. Big Duh! moment for me. I snatched up some un-notched Fiskars blades for it at Joann's a few weeks ago and put my little red baby back to work and just went to town cutting up flannel scraps. I was stiff & sore that evening! I was enjoying my old gadget so much I didn't realize how long I worked. There is no way I could have cut up all my flannel scraps with one of my Olfa cutters in a single session.