I had a free-flow filter before, but it was a K&N type (flat like the factory one). This one, with its cylindrical design, increases the filtering surface by 200%. My Duke gained crazy "breath" and torque, both at low and high RPMs (I also have a free-flow exhaust). The build quality is such that K&N should be ashamed, while the fitment is like the best factory one. It's also Greek - finally, a time when the Greek didn't go abroad to shine...