UC-206 Speed-Spec Axle Bearing (Blue Rubber Seals)
 
So these are aimed at folks who want a 'better steel bearing, something a little less expensive than say a 'best' / ceramic hybrid bearing but something built to the very high standards and tight tolerances normally only found in bearings double the price. As such, their name: "Speed Spec" built to specs designed for speed. These sport rubber seals so folks can clean / re-lube . . . make last longer / run smoother.
 
Higher quality bearing designed for speed.
Has Removable Rubber Seals
Has three set screws