model: 604 ZZColour: silverMaterial: metalSize: 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: 20pcs x BearingsOnly the above package content, other products are not included.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.