ABEC rated bearings have precision ground and polished raceways made from hardened chrome steel. Their internal tolerances are even greater than semi-precision bearings which make them capable of even higher speeds, higher load capacities, and longer life. The high internal tolerances and polished raceways make the bearings incredibly smooth and almost completely silent in operation.
Plastic Housed bearings consist of a radial ABEC bearing inside a polypropylene housing assembly. The outer housing fits easily into tubes without damage to the radial bearing. The housing must be crimped into the tube which means they are not replaceable. The inner adapter allows the bearing to fit onto different axles, usually hex shaped. It also prevents metal-on-metal contact between the bearing and the axle which means these bearings are even quieter than other styles of ABEC bearings.
Many people mistakenly think these bearings are all plastic. Commonly they are referred to as “Roller End Caps”.
