A single mass of premium AL-7050-TV alloy is pushed, pulled and squeezed into a hollow crank arm. Result? Supreme strength without the tank-like weight. We weren't the first to fabricate hollow crank arms. But we're the best. You won't find a higher stiffness-to-weight ratio. Our Open Core Technology cranks are stiffer, stronger, and lighter weight than any solid forged crankset. GXP's Gutter Seal design cuts friction, durability and weight-improving both feel and performance.