MACH-1 RACING miniature deep groove can also be classified as "Open", "Shielded", or "Sealed" depending on the existence and type of seal or shield. Deep groove ball bearings have two inherent advantages;
They can sustain some axial load in either direction as well as radial loads, and;
The two raceway cross-sections are simple circular arcs which can be very precisely finished so the bearings have low friction and very little noise or vibration.
 
Several different cage designs are available with different characteristics and the choice depends upon the individual application.