ROTOR Round Rings DM 2x. The Round Direct Mount Chainrings. The Direct Mount is CNC’d from a block of 7075 aluminum to save more than 30 g over a standard chainring combo which, together with ALDHU crank arms, becomes ROTOR’s lightest crankset ever. The ALDHU 3D's innovative modular structure makes each component individually available to accommodate the current spectrum of riders and bike standards.