The pro 4 rear hub 135 x 10 sstrials from hope is a single 6 speed version of the pro 4 that comes supplied with spacers for a single speed conversion that has become a popular and obvious choice for some of the best trials riders in the world with more engagement points and hopes proven reputation for bullet proof quality you have the security that this will be the heart of a strong and reliable wheel it runs on sealed stainless steel cartridge bearings with a 10 x 135mm axle with a 4 pawl