Hybrid Ceramic Bearings for the front hubs.
Featuring chrome steel races, ZrO2 Ceramic Balls, nylon cages and oil lubricated.
These are extremely free spinning, lightweight, and require little maintenance.
Available in 2 popular sizes as direct replacements for most front hubs:

.625 id x 1.375 od x .4375 wide
.750" id x 1.625" od x .4375" wide