Small but important - skateboard bushings
The skateboard truck bushings are quite a small part of your whole board but that does not mean they do not have a big role in how the board rides. You would find two bushings on each truck - a top bushing and a bottom one. The top one faces the street and the bottom faces the deck.
Material and hardness of the bushings for skateboards
All bushings are made of polyurethane, which in normal language will say a certain type of plastic which is quite heat resistant.
However, that does not mean they are all the same. Truck bushings, just like the wheels on your board, come in different hardness. This hardness is also measured in durometers, which is given as a number up to 100, followed by the letter A. The higher the number, the harder the bushing.
Skateboard bushings are normally a bit harder than longboard ones, for example since softer bushings mean more steering while the harder ones allow more stiff and controlled board.
What shape bushings to choose?
Bushings come in two main shapes - cone and barrel but there are few varieties stemming from those two. Normally in skateboarding, you would go for a cone top bushing and barrel bottom bushing. Cone bushings give more mobility and steering while barrel bushings give a harder and stable ride.