There is a series of "Spring Pad"s n 4 mm increments, for the front and the rear. They are identified by a set of raised bumps on one end.
"1 dot" through "4 dot".

They fit between the top of a spring and the top spring perch, fine-tuning the ride height.

Their original purpose was to offset sag from older springs.

Search for "R170 Spring Pads".