Ceramic Hybrid Bearing 5x11x4mm (2) fit Losi HPI Tamiya Axial Ky
[smr115czz]

Ceramic Hybrid Bearing 5x11x4 (2) pcs
High quality ABEC-5 grade made of  AISI440C stainless steel races Harness 50-55 and Si3N4 ceramic balls, light oiled 5x11x4mm low friction bearing . ZZ double metal shields,
Rubber seals are great protectors against dirt but the is that they offer a little more friction due to the tighter seal, may it came off out the bearing when running extremely high speed. the performance of a metal shield is excellent but can allow fine dirt to get in they are  the best performance you could attain while maintaining some protection from dirt.
 ZZ metal shield ball bearings 5x10x4mm MR115CZZ ABEC-5
They are also most competitive Ceramic Bearings on the market.
Ceramic hybrids are lighter, capable of achieving higher RPM and sustaining higher operating temperatures than traditional bearings.
Ceramic Bearings can run faster than all steel bearings due to the lower centrifugal force generated by the ceramic balls, the speed increase for Ceramic Bearings is 35% with adequate lubrication.Ceramic Bearings are less subjected to ball skidding under initial acceleration.This allows the bearing to last longer and be far more reliable. Low heat expansion allows the bearing retainers to last longer.