Our patented OPI 3D forging process enables us to build hollow, seamless crank arms that are not only extremely light but also incredibly strong and stiff. In fact, they are the stiffest, strongest crank arms we've ever made. Lighter and stiffer than the competition and completely compatible with every HollowGram spider and chainring set-up, the HollowGram Si cranks bring top-level performance to more price-points.
