Griffin Skateboards Axcelspring Washer Cups. These machined from 303 stainless steel washers have an inside lip that locks tight to the kingpin. The center sleeve puts the pressure on the center of the bushing giving it more energy. The facing is the rings on the top and the bottom that gives extra grip to grad onto the base plate and the bushing. No movement equal straight power.
More info at www.griffinskateboards.com