Steel and Ceramic: Made of high quality steel and ceramic, these miniature bearings are low noise, and reliable for . High Efficiency: The inline roller bearing has a compact structure, and the balls can make the bearing rotate faster while working, and consume less energy to maintain its speed. Good performance: Ceramic ball bearings have better resistance and rarely require lubrication. Keeping the bearing clean and dry, and maintaining it with lubricating oil regularly can effectively prolong the life of the bearing. SPECIALLY DESIGNED: These single-sided shielded ceramic balls run smoothly and with low friction during operation. They are designed for inline skates to increase speed. Specifications: size: 11.7 x 8.5 x 2.2 cm Material: steel + ceramic colour: As shown Package Contents: 32 x bearing Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.