These are instrument grade ball bearings. The first number is the bore size and the second number is the outside diameter. All units are in millimeters (mm). The letter N and P indicate quality class. N is normal and P is precision.
The P class bearings are made per order so lead-time typically runs about 9-12 weeks.
Product catalog can be found here.
Click here to download 3D CAD data in STEP file format. Data for all available FMB products is contained within one ZIP file.