Wright pulleys are split steel construction for low inertia and cool running belts. Pulleys are made from a round disk of steel, and a rolling knife is very precisely rolled into the edge of the disk to form the perfectly round V groove. This method makes a pulley that conducts heat away from the belt quickly and, because it's strong and approximately 20% less inertial* than a cast iron pulley, the clutch last longer. All deck pulleys are approximately 1'' larger than other brands, which significantly reduces belt tension and flex.