BRONZE
GRADE

high-speed bearings


Precision steel ball bearings
Nylon retainer cage  
Single removable rubber shield 

Silver
GRADE

Six-Ball bearings


Six Precision steel balls
Nylon retainer cage
Single removable rubber shield 

GOLD
GRADE

ceramic bearings


Precision Ceramic Balls 
Coated Races 
Nylon retainer cage 
Single removable rubber shield