I recently aquired an abused 86? 600 rear mech with a trashed jockey pulley with a ceramic bushing (the idler pulley is a retro-fitted Suntour!). The teeth are worn down to slight bumps -- i guess the chain was misaligned for a while. I was going to stick another non-ceramic g-pulley in there from parts I had, but I realized I had no spare 'Centeron G-Pulley', only idler pulleys. Is there a difference besides the slight raised edge found on the g-pulley and what does it do? Can I buy ceramic pulleys from somewhere?