according to the instructions i recieved with springs, the stock spacer should be cut down to a length of 4.25inches. I BELIEVE THIS IS AN ERROR!! I had absoluterly NO sag with this length and eventually cut spacer down to 3 1/2 inches, about 86mm. very pleased with the improvement. also NOTE: while stock springs are installed with close-wound coils DOWN, the Progressives are to be installed close-wound coils UP.