You are buying a set of 8 lowest friction 608 Ceramic Bearing, the bearing has only 4 silicon nitride ceramic balls, 4 balls made the friction less and less, with high quality PTFE cage, bearing is made of Chrome Steel with 4 Si3N4 Ceramic (Silicon Nitride) balls.

• Item: 608 Ceramic ball bearing
• Type: High Clearance radial ball bearing
• 4-Balls: Si3N4 Ceramic (Silicon Nitride)
• Closures: Open
• Clearance: High Clearance (C4)
• Cage: PTFE
• Dimensions: 8mm x 22mm x 7mm/Metric
• ID (inner diameter)/Bore: 8mm
• OD (outer diameter): 22mm
• Width/Height/thickness: 7mm
• Size: 8 x 22 x 7 mm
• Quantity: 8 Ball Bearings