Bearings reduce friction by providing smooth metal balls or rollers and a smooth inner and outer metal surface for the balls to roll against. The balls or rollers "carry" the load, which allows the device to rotate smoothly. Specifications: MR126ZZ Size: 6 x 12 x 4mm (inner diameter x outer diameter x thickness) Package Included: 100pcs x Bearings Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in a little different from the real thing. The measurement allowed error is +/- 1-3 cm.