10-Pack 8x13x4 Shielded Miniature Bearing8 x 13 x 4 Shielded Ball Bearings Lot of 10 Bearings 8 x 13 x 4 Shielded Ball Bearings, made from durable 52100 alloy steel, commonly known as chrome steel, each Comes with double metal shields (ZZ) to keep out dust and dirt, additionally, these bearings come pre lubricated with grease for smooth operation, Bearings are packed 10 bearings in one plastic tube. 8 x 13 x 4 Ball Bearings Deep Groove Ball Bearings Size: 8mm x 13mm x 4mm Inner Diameter: 8mm