Dyna Hub: The PD-8X is the union of a precision 6V3W dynamo with the modern 15mm thru-axle(6 bolt or centerlock) disc specification …and the new acme of dynamo technology for “Xtreme” use. It is perfected integration of “bleeding edge” technology and muscular aesthetics. Yet the ultimate attainment of 8X remains its superior mechanical performance. Not only the most efficient in its class, the 8X is also the lightest in weight. With premium surface treatment and design, the 8X is gorgeous in motion and striking at standstill.