Is this Sora rear derailleur (rd r3000 gs) actually compatible with 8 speed cassette or is it seller mistake? Can't find any other information online. : r/bikewrench
Amazon.com : Box Four 8 Speed 11-42T Wide Multi Shift Groupset with Rear Derailleur, Shifter, Cassette, Chain, Shift Housing Kit Components Mountain Bike Drivetrain Upgrade : Sports & Outdoors
Shimano Deore RD-M591 Rear Mech Black SGS
shimano - Can we use a 9 speed rear derailleur on a 8 speed bike? - Bicycles Stack Exchange
SunRace 9-speed Cassette - C&L Cycles
10 spd clutch derailleur conversion for 9 spd - Pinkbike Forum