Shimano ZEE RD-M640-SS Rear Derailleur - 10 Speed, Short Cage, With Clutch

great authentic Shimano product. have it working with a 11x42 cassette without any modifications (1x10) with Zee shifter;

I paired this with a Zee 10spd shifter and a 1x10 drivetrain and took it over some very bumpy trails. No dropped chain and it shifts precisely. Worth the purchase;

My old retro bike with ZeeDH and Box 4 8 speed shifter. This thing rips. I normally ride single speed but I decided to try some road bike gearing on a old 1990's balance frame. 26th front 12-19 gears out back. This thing climbs great out of the saddle. So if you want to run the Zee derailer on 8 spd the box 4 shifter is your jam!;

I’ve been running an original Sram X7 long cage for a couple years on a 1x10 conversion. My local shop recommended the Zee but it was backordered so I was lucky to find it on Amazon. Best decision I’ve ever made. No more dropped chains and shifts extremely quick and crisp. I was able to change it out and get it adjusted pretty easily after watching a few YouTube videos. Out of box it feels sturdy and well made. I highly recommend;

I was new to mountain biking and this was going on my Cannondale catalyst 4 hardtail. For the money this is one of the best derailleurs you can get and I can say that with confidence. shifts extremely smooth on flat and on slight inclines for more harsh inclines it will still shift it just doesn't like it too much. However behind that and the relatively small range cassette. I have no complaints. if you are looking for something for the trails where there will be a lot of climbing you might want to steer away from this but if you are up for building some serious muscle it is good. Like I said in the title I have run this since 2020 and have had zero problems with it. The durability is also extreme it can take a real bashing and it has taken several rock hits and come out okay.;