Hollow Kingpin - Lightening the load, hollow kingpins reduce weight for lighter feeling trucks, while still maintaining strength in this critical area.
Hollow Axle - Hollow axle trucks cut down on the materials used in the axle, so your trucks feel lighter, because they are lighter.
Sizing Reference
Note - Every skate truck brand represents their sizing a little differently, so it's easy to get confused. Take a look at this graphic and then reference the size chart.