How to determine which derailleur hanger will do the job on the lower RD that the mounting plate on the upper RD did ? There are so many… my frame has no
Derailleur hanger types? How to find it? What is dropout? - Elanus Parts
Complete guide to rear derailleurs: everything you need to know - BikeRadar
shimano acera rear derailleur hanger off 78% - medpharmres.com