Each skate truck has a lower and upper urethane rubber bushing which allow the truck to pivot and turn the skateboard. Bushing are usually sold in sets with 2 lower and 2 upper bushings in a range of hardnesses which are measured in durometer. Lower duro bushings are softer will require less effort or weight to make the truck turn and higher duro bushings are harder and will give a more solid ride. At NOTE we stock a selection so you can repair worn out old bushings or replace stock bushings to personalise your ride.