Adjusting your shock's spring rate can profoundly improve your bike's handling and suspension. In fact, you may find yourself using different spring rates for different trails, depending on the conditions and type of trail. Or you may increase your spring rate for long climbs and decrease it for down hills.
There are three different Sprindex lengths and strokes available, and each Sprindex coil can be adjusted through a certain spring rate range. Be sure to use the correct included adapter as described. Make sure that the spring length fits on your shock and that your maximum shock travel is not more than the specified Sprindex coil travel.