It is better to use the Martelli blades in their cutter. You can use Olfa, but the center in the Olfa has those notches and the will sometimes make the cutter "pop" as you use it. They tell me that eventually the Olfa blades will saw through the center screw. I got rid of all my Olfa blades and bought a huge pack of Martelli blades and split them with the other 5 ladies in my church quilting group who also have the Martelli cutters.
I love my cutter, it does work a little better with their own blades.