Made in USA Black Ceramic Ball. Exclusive 6 ball design in-line bearing. Exclusive design 6 ball nylon retainer with self-lubricated material. Inner ring with exclusive design “SCRS”, S-channel Rubber Shield, to avoid contamination. Clearance designed for in-line racing. Greater loading than standard 608 bearings. Lubricant: TK Ultra Light Gel for better protection inside balls and nylon retainer. These bearings are rebuildable after a few years of hard use. They will have to be sent back to Twincam with a small fee.