BRONZE
GRADE

high-speed bearings


Precision steel ball bearings
High-Speed Nylon retainer 
Single removable rubber shield 

Silver
GRADE

Six-Ball bearings


Six Precision steel balls
High-Speed Nylon retainer 
Single removable rubber shield 

GOLD
GRADE

ceramic bearings


Precision Ceramic Balls 
Coated Races 
High-Speed Nylon retainer 
Single removable rubber shield