As always depends what you want to do with them. Reds are fine for the street and racing, yellow if doing circuit work alone. From memory, reds all the way up was equivilant to yellow half way. In reality you will set them and forget about them unless you are racing. Adjustment is easy, just pull off at the bottom, push up to full compression and turn them. As they are rebuildable (and re valveable?) they should last the life of the car. Don't waste too much money on springs, as they are something you probably will change along the way. Dare I say it, ring David Lawson at AJPS, regular on this site.