608 ABEC-9 precision hybrid ceramic bearings are suitable for applications like skateboards and inline skates. These bearings use 7 black ceramic beads (Si3N4) and a high-speed nylon cage designed for durability and high-rev capabilities. They are engineered for speed, with a limiting speed of 22,000 rev/min, do not require grease for operation and are known for super high speed and long spin time. 8 Pack.