Each set contains 4 universal stainless steel washers for bushings or wheels. The washers are highly recommended for anyone using non-backless bearing wheels. The purpose of them is to put them between the truck and the wheel in order to increase durability. As you may have noticed, the area on some trucks where they come in contact with the wheel can be rough, increasing wear on your wheels.
These washers provide a smooth surface for the wheels to roll against, increasing the lifespan of your wheels. These washers can also be used with bushings.