Rotor's 3D Plus Road crank is a revolutionary design in the world of carbon versus aluminum components. Using Rotor's Trinity Drilling System and 7055 alloy, it is stiffer than most carbon cranks, and it is also compatible with virtually any bottom bracket system. The Rotor Flow Aero Cranks, based on the 3D Plus, therefore is a paradigm changing crank designed for both road and pure TT bikes. The Flow Aero features the same proprietary Trinity Drilling System TDS as Rotor's 3D cranks. This process drills three full depth holes from axle to pedal, which leaves behind a structure similar in form to box bridges. This is unlike a classic hollow tube crank design, due to two additional interior walls left over after drilling. This gives the crank arms an exceptional strength to weight ratio. Unlike the 3D cranks, the Flow features a smooth exterior and a shape that widens slightly as you move from the spindle to pedal. A crank does not fully intersect with laminar airflow while riding. This is due to the fact that the front wheel and fork have already cut through the air and the turbulent air that meets the cranks has less resistance than unbroken air. Because of this, the smooth surface of the crank excels to be even more aerodynamic. It gives a six second time reduction over a 40k TT at 200 watts, and in a race that is often won by seconds, this advantage could mean a place on the podium. Its design is worthy of both pure time trial frames, as well as your lightweight road frame. Please note that the chainrings are not included with this crankset. The QX rings are recommended, though you may use Rotor's round rings if your preference is toward classic shape. The Rotor Flow Aero Cranks are available in sizes 110 170mm, 110 172. 5mm, 110 175mm, 130 170mm, 130 172. 5mm, and 130 175mm. They come in the color Black.