I have the Mulfab and it has made a lot of difference to my 4/4 sport which had soft main springs. It does not now hit the bump stop as it did regularly before and the ride height has been raised by half an inch which is great on my drive and speed bumps. Also it is a lot cheaper than the Supplex.It has also stopped the front end "nodding" on undulating roads thus giving a smoother ride. I think it would be OK on Norwegian roads which from memories of driving around Bergen can be quite challenging.
