Perfect fit for 20 year old Genie Pro screw drive. Very similar to the original factory part, the set screw is on the opposite side and the switch is black instead of white, but this does not affect function. Came in an ordinary white box with no markings and no instructions which led me to suspect authenticity but so what; worked well and wasn't too expensive. Installation is easy and fairly obvious, but if you want to be sure there are YouTube videos that explain it. I'm glad I got it and saved myself an expensive professional repair. So cheap and easy. Now that I've replaced the broken upper (upper) derailleur, I'm considering ordering another to do the lower one before it fails with age. Order two and make yours in one go.