Rotor has devoted itself to a new line of mountain bike cranks it's calling REX, and they are based on the same successful Trinity Drilling System as all Rotor cranks. The REX 1. 1 is for a 1x drivetrain. The Trinity Drilling System TDS 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. The TDS creates a maximum strength to weight ratio, and the arms were 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 489grams. The Q factor is 163. The Rotor REX 1. 1 Cranks are available in sizes 170mm, 172mm, and 175mm. Please note the REX 1. 1 does not include a chainring.