REX is the designation given to Rotor's new line of mountain bike cranksets. Using the same technology as its lightweight aluminum cranks, they are setting new standards in strength to weight ratios. The REX 1. 2 is its double ring crankset that will have you powering up and down your local trail. Use it with Rotor's Q rings for an even greater advantage over the competition. The REX cranks use Rotor's proprietary Trinity Drilling System TDS. This is a method of hollowing out the cranks, which reduces weight and maximizes stiffness. Unlike traditional hollow crankset design, the Trinity Drilling System drills three channels from the pedal to the spindle. While these holes remove excess material, they also leave behind two thin walls, making them stiffer than the design of a single hollow chamber. Ultimately, the design is similar to that of a box truss bridge. The arms are constructed using a new 7055 alloy, which is both lighter and more durable than the more often used 7075. UBB30 UBB24 axles ensure maximum frame compatibility. Without the bottom bracket they weigh in at roughly 505grams. The Q factor is 163. The Rotor REX 1. 2 Cranks are available in sizes 170mm, 172. 5mm, and 175mm. Please note the REX 1. 2 does not include chainrings.