Trucks are the set of metallic components located under the skateboard. They allow for the skateboard to turn and grind. One truck consists of a hanger and a baseplate, held together by a kingpin. Trucks are attached to a skateboard with hardware at the baseplate. Wheels (equipped with bearings) are attached at both ends of the hanger (on the axle) while polyurethane bushings are included on the kingpin to facilitate turning. There aren’t many variables to consider when selecting trucks. Some have hollow axles. Some are made from lighter materials.
The most important thing is to select trucks with axles sized to match the width of your board (deck). Unfortunately, all truck companies have their own way of indicating axle lengths. Refer to this sizing chart for clarification.