Review on 🔧 BOX COMPONENTS Four Rear Derailleur 8 Speed Wide Cage Black: Efficient Shifting Performance in One Size by Alex Montgomery

I bought this to upgrade my nephew's bike (Trek 930 Singletrack) to a 1x drivetrain with more rear cassette spacing. 11-40T Sunrace. Unfortunately, this derailleur cage isn't long enough to clear the last two rings of the cassette unless you use a derailleur extender. I used a Wolf Tooth RoadLink derailleur extension and it was enough to free a 40T ring. The nephew is very happy with his bike and the gearbox, four 8-speed rear derailleurs and gear combination work well. You will likely need to add a link or two to the chain if you upgrade to a larger cassette.