After years of testing, from daily driving to harsh off road terrain, Heavy Hauling and everything in between. We now have available the Kryptonite 2.5" Dual Rate Leveling Coil Spring set. This is the most durable and premium spring option on the market. Designed with heavy duty truck use in mind, this spring provides rugged load handling capabilities while maintaining an extremely comfortable ride. Our true Dual Rate spring can provide the best of both worlds. Using top rated material we have produced a plush ride with minimal spring sag. Mile after mile our springs will hold up. to any truck, and any job.