1. Product Overview B31-13 non-standard single-row open deep groove ball bearing, overall dimension 31mm inner bore × 54mm outer diameter × 13mm width, fully interchangeable with original NSK B31-13 and equivalent HTFB31-13E, widely matched to Japanese CVT intermediate auxiliary shafts and miniature differential assemblies. Open design without rubber seals, equipped with stamped low-carbon steel cage and factory standard C0 internal clearance, C3 clearance customizable on