Bones Hardcore Black Skateboard Bushings - Includes 4 Pieces - Medium. Bushings provides flexibility and easy adaptability for your skateboard trucks. The typical skateboard truck has two bushings on each truck, one that keeps the truck springy for easy turns and a smaller one beneath the kingpin that is easily tightened or loosened to adapt to your style. Tighter trucks work best for mastering tricks while looser trucks are best for carving down the street.