A replacement centre case gearbox for the GU old style multipoint door lock mechanism. If you're having problems with your door lock, the gearbox is almost always the problem and changing it is as simple as removing a few screws. Product Information Important Measurements: 35mm Backset / 92pz Centres This is the mechanism inside the door that is operated by the handle. Most likely to be the problem when a lock fails. Reversible latch for left or right handed doors