Bbb rollerboys ceramic jockey wheelsreplacement rollerboys derailleur jockey wheels equipped with low friction ceramic bearings for ultra smooth glide and exceptional durability made from grivory composite material provided by ems swiss grivory is the proven material for metal replacement features lubricated with special ceramic light oil for extra smoothness composite material provided by ems swiss with 40 glass fiber complete set of bushings for different shifting systems included 11t c