For high-speed machining centers and milling spindles, the KTNHA/HC5-SP are single-row, silicon-nitride, cylindrical-equipped roller bearings. According to the manufacturer, the bearings' centrifugal force is low because the cylindrical rollers are lower in density than standard steel rollers, resulting in less friction.

They are also reportedly about 50% faster than conventional steel-roller bearings and 50% narrower and twice as rigid as standard ceramic-ball bearings.

SKF Machine Tool Precision Technologies
Bethlehem, Pa.
skfpt.com