TheRace Face Turbine Crank Armsare deep pocket forged and CNC machined to create incredible durability and stiffness. The proprietary Cinch system removable spider can convert between existing chainring standards and Direct Mount spiderless rings. Race Face Turbine Crank Arms Features Industry standard 30mm spline interface, CNC machined from 7050 Alloy Compatibility with the Race Face Cinch Power Meter Cinch system: choose a spider or use a Race Face Direct Mount Narrow Wide Ring Race Face Direct Mount Narrow Wide Chainrings Interface (BB): Cinch Race Face Cinch Bottom bracket is sold separately Length: 170mm or 175mm Made in Canada