1/4″ individual Si3N4 ceramic ball – Grade 3
Silicon Nitride full-ceramic balls are normally used in Shimano and/or Campagnolo Wheels using Cup & Cone technology. In comparing cup and cone technology to a sealed bearing, you can equate the (a) outer race of a sealed bearing to the (b) inside of a hub (or cup) of ‘cup and cone’, and, (c) the inner race of a sealed bearing to the (d) cone of a ‘cup and cone’.
For cup and cone hubs to work perfectly, they need to be rebuilt at least every 6 months. When rebuilding for the first time, make sure that you clean out ALL of the old grease from the entire hub and axle assembly. (Note: seals are easily bent and/or damaged. If you want to reuse them, be extra careful when removing and replacing them, or, better yet, go to your LBS and purchase 4 new seals for use when reassembling.)