model: 604 ZZ Colour: silver Material: metal Size: 4 x 12 x 4MM(Inner Diameter x Outer Diameter x Thickness) Bearings reduce friction by providing smooth metal balls or rollers and a smooth inner and outer metal surface for the balls to roll against.These balls or rollers "bear" the load, allowing the device to spin smoothly. Package Included: 10pcs x Bearings Note: Light shooting 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.