The pulley wheels are the fastest spinning bearings on your bike. An upgrade to ceramic bearing therefore is the most effective upgrade. C-Bear ceramic pulley can be used both for road, cyclocross and MTB.

Full Ceramic Pulley Shimano Sram|Bi-cycle bottom bracket with ceramic bearings|c-bear.com Pulley Full Ceramic

Shimano-Sram
Campagnolo
Pulley - Titanium |Bi-cycle bottom bracket with ceramic bearings|c-bear.com Pulley - Titanium

Shimano-Sram
Campagnolo
 
Pulley Campagnolo|Bi-cycle bottom bracket with ceramic bearings|c-bear.com Pulley Campagnolo

11 Speed
Pulley Shimano-Sram|Bi-cycle bottom bracket with ceramic bearings|c-bear.com Pulley Shimano-Sram

Aluminium
Carbon
Delrin
Pulley - XX1 Sram|bi-cycle ceramic bearing|c-bear.com Pulley - XX1 Sram

Sram 11 Speed
XX1
XO1
Force CX1
Force 1
Rival 1