105 mm x 145 mm x 20 mm ISO NP1921 cylindrical roller bearings

YOU’LL NTN BEARING CORP.OF AMERICA FIND AN EXTENSIVE SELECTION OF 580.0000 mm D 105 mm x 145 mm x 20 mm ISO NP1921 cylindrical roller bearings 105 mm x 145 mm x 20 mm 280.000 mm d FOR SALE.

What is NP1921 bearing cross reference？