20 MR84ZZ bearings. 8mm outer diameter. 4mm inner diameter. 3mm thick Wide application on electronic equipment, power machinery, medical devices, printing equipment, textiles, etc. Includes 2 shields in metal to protect the bearing from dust or any possible contamination Well oiled, shows firmness and robustness. If you want a lighter movement, just spray with a light degreaser Product Description 20 high quality MR84ZZ small bearings with GCr15 steel balls < p>4 x 8 x 3 mm Small bearing for prototypes and inventions. It can be used in clean 3D designs and other mechanisms or engineering. Bearing dimensions: Inner diameter: 4mm Outer diameter : 8mm Width: 3mm (Well-oiled factory, proof of firmness and sturdiness. If you want a lighter movement, just spray with a little light grease.)