| Bearing Type | Ball |
| For Load Direction | Radial |
| Construction | Single Row |
| Seal Type | Shielded |
| Part Number | 638ZZ |
| For Shaft Diameter | 8mm |
| Bore Dia (d) | 8 mm |
| Bore Dia Tolerance | -0.008mm to 0 |
| For Housing ID | 28mm |
| Outer Dia (D) | 28mm |
| Outer Dia Tolerance | -0.008mm to 0 |
| Width (B) | 9mm |
| Width Tolerance | -0.12mm to 0 |
| Ring Material | 52100 Chrome steel |
| Ball Material | 52100 Chrome steel |
| Cage Material | 300 Series Stainless Steel |
| Shield Material | 300 Series Stainless Steel |
| Dynamic Load Rating (Cr) (Newtons) | 3879 |
| Static Load Rating (Cor) (Newtons) | 1586 |
| Max Speed (Grease) (X1000 RPM) | 28 |
| Max Speed (Oil) (X1000 RPM) | 34 |
| Lubrication | Required |
| Shaft Mount Type | Press Fit |
| Temperature Range | -30° to 110 °C |
| ABEC Rating | ABEC-1 |
| Radial Clearance Trade No. | C0 |
| Radial Clearance | 0.002mm to 0.013mm |
| RoHS | Compliant |
| Ball Qty | 7 |
| Ball Dia | 4.7620mm |
| Weight (grams) | 30.3 |
