The flap back hinge lets the door fold back on itself as it travels the curve of the track. Which version you need depends on whether the door is automated or hand operated.
Signs it needs replacing
The door binding at the curve of the track
Visible bend or fatigue in the hinge plate
Sizes and variants
Variant
Specification
Automatic
For motorised doors
Manual
For hand operated doors
Fitting notes
Automatic and manual versions are not interchangeable. Fitting the wrong one puts the load in the wrong place and the hinge fatigues early.