The typical skateboard truck has two bushings on each truck. Bushings are rubber rings found inside the trucks that cushion the trucks when a skateboard turns. The stiffer the bushing the more stable the board. The softer the bushings the easier it is to turn a skateboard.
Be sure to change your bushings frequently in order to keep your skateboard responsive to your personal skateboarding style.
Plain and simple, the Downhill Double-Barrel Bushing Pack is built for speed. Double barrels, teamed with cup washers can give your setup that fully locked in feel that gives you the confidence you need to grab some serious velocity.