This is the clutch Diaphragm spring that was used for the more powerful motors, starting with the R90 S and on through the R100 Models up to and including the 1980 model year.
Dimensionally, this is the same as the diaphragm spring used in the earlier, less powerful models, part number 2121288. This spring can be installed in any bike from /5 to 09/1980 production, the tension will however be greater and the lever pull much harder.
If you have installed a Siebenrock Power Kit on your R75 then we do suggest using this heavier spring. Also if the harder lever pull is not something that concerns you, in that case also opt for this spring.