Shimano Acera RD-M3020-SGS Rear Derailleur - 7/8 Speed, Long Cage, Black

I needed a long cage derailleur to accommodate an 11-40T Shimano cassette. The installation was easy and fast. By following the instructions from the following video on Youtube by Park Tool, "How to Adjust a Rear Derailleur – Limit Screws & Indexing," the derailleur performs well. The shifting is on point, quiet, and smooth. I am very satisfied with the derailleur.

Easy to install and adjust. Works perfect even dirty from muddy trails

Upgraded drivetrain on wifes Aventon LEVEL II from 8 speed 12-32 cassette to 11-40, needed a derailleur to accommodate the larger cog. Works perfectly! (Recommended)

Smooth shifting, excellent quality

The cheap derailer that came on my Lectric Ebike skipped a lot and I could not adjust it to work better. Although this is a lower level shimano, it works perfectly on my Ebike and solved the skipping problems. Great value for the money.

works well

It’s often been remarked that Shimano doesn't make any bad products, and their cheapest brakes and derailleurs work just about as well as their most expensive ones. I certainly found that true of this unit. I used it to replace a 25 year old Deore MTB shifter, and if anything, it’s smoother than the old Deore, and has a significantly wider range. I’m running a 2x8 with 38-24 in front and an 11x34 cassette, and this easily wraps all that chain and could certainly handle more.

Swapped it in a banged up one on my specialized roll 2.0 sport - looked for an upgrade and my gear changing is perfect now (one slight click and a perfect change)(also through on a new chain - runs like a dream now). Would note that I also bought a new derailer hanger - they are designed to bend first so if you are upgrading an old one that's been dropped a few times you probably need a hanger too (they are about $10-$15 and specific to your bike).