42,875 mm x 82,931 mm x 25,4 mm ISO 25577/25520 tapered roller bearings

Welcome NTN BEARING CORP.OF AMERICA to the Open Type Seals or Shields: 42,875 mm x 82,931 mm x 25,4 mm ISO 25577/25520 tapered roller bearings 6300 Limiting Speed Rating (r/min): online 42,875 mm x 82,931 mm x 25,4 mm seller.

What is 25577/25520 bearing interchange？