Some time ago I purchased Progressive fork springs (11-1521) for the GL1800 thinking they would also fit the F6B.

Now I've come to fit them I realize Progressive don't list them for the F6B.
I fired off an email to Progressive Suspension and they replied straight away advising against using them as the F6B is lowered?

I guess this is now why there are three different monotubes, one for each model of bike including a 1" lowered F6B.

What I don't understand is Honda list the same part number for the OEM fork springs for each bike.

What could the difference be?