Custom Works Short Course Big Bore Shock Spring Set. Racers looking to tune their Short Course trucks for dirt oval racing have to look no further than this spring assortment. Proudly made in the USA means these springs are consistent in rate from one spring to the next but also the spring will not fatigue and become considerably shorter with use like some other springs offered of lesser quality. This spring kit offers rates of 5, 6, 7, and 8 pounds which should account for all your needs on typical dirt oval tracks.