Sprindex Adjustable Rate Coil Spring 75x162mm - 510-570lbsAdjustable base spring rate by changing the length of effective coils Includes spring, adjuster, and 5 Delrin performance adapters that allow the spring to spin while compressing and also adapt to a variety of shocks on the market Coil is made of super high tensile spring steel similar to "lightweight" springs (which is why Sprindex is lighter than regular springs) in order to handle the stress of the system when adjusted to its highest spring rate