8x19x4.5mm Ball Bearing - Shielded - MiniatureBall Bearings 8mm x 19mm x 4. 5mm Ball Bearings, a standard bearing size with dimensions commonly used across many industries: 8mm x 19mm x 4. 5mm. Made from high strength chrome steel for durability and performance, each Comes with double metal shields (ZZ) to keep out dust and dirt. Double Shielded Ball Bearings Size: 8mm x 19mm x 4. 5mm Dimensions: 8*19*4. 5 mm Metric ID (inner diameter) Bore=8mm OD (outer diameter)=19mm Width Height thickness=4.