Fly Magneto Female Rear Cassette Hub - RHDFly's Magneto Cassette hub features a magnetic system engage using the force of two magnets that allows the ratchet ring to engage. The magnetic field provides an even repelling force which makes the ratchet to work completely straight and are created in a way that reduces friction compared to the use of springs. The Neomidium magnets Fly use maintain the magnetic field pretty much forever, as well. These properties creates the fastest, most reliable