The Genie screw drive carriage assembly with magnet has teeth inside it that connect to the screw inside the garage door opener rail. The carriage teeth gripping the screw allows for smooth operation of running the garage door up and down the rail. If the motor on your garage door opener is running and the screw drive is turning, but the garage door is not operating (you may even hear a grinding or chattering noise), then it is time to replace the screw drive carriage. Works with magnetic or mechanical style limit switches  Lever for emergency release cord to attach to keeps you safe in case of a power outage or other emergency to release the door quickly  The carriage is designed to protect the screw drive from wear and tear Genuine Genie replacement part  The carriage is often referred to as a Genie trolley Easy DIY replacement, the screw drive carriage even has an arrow pointing to the door to make sure it goes on correctly (check out this blog article with instructions and video here) Direct replacement for previous/ discontinued carriage parts numbers- 36179R, 34107R, 34107R.S, 20414R, 25589R, 25589S This same screw drive carriage was used in many older model Genie garage door openers over the years. See the list below.  Compatible with Models:  1060, 1560, 2560, 3560, 3860, IS525, IS525/B, IS550, IS550/B, IS850, IS900, IS900/B, IS920, CM7500, CM7600, CM8500-S, CM8600, PRO95, CM8600-FN, H4000, H6000, IS525, IS525/B, IS550, IS550/B, IS850, IS900, IS900/B, IS920, 2060L, 3060L, IMS1000, ISL950, ISL950/B, ISL980, ISL980/B,  G4050CL, G5000CL, G5050CL, G5500CL, G5700CL, G8000CL, GX9000CL, GXL9500CL, GXL9550CL, GXL9900CL, GXL1000CL,Excelerator, H8000-07, H8000D, ISD990, ISD995, ISD1000, PRO99-2IC, PRO99FN, CMD9900, 4560, 4060L