Version 2 of the BSD Substance XL cranks including B. A single bolt 2.5 piece crank with hefty a 24mm XL spindle and a flush boss design eliminating sharp edges around the ankles. Features heat treated 4130 XL 24mm diameter CNC machined 48 spline hollow spindle and heat treated 4130 chromoly arms with rectangular cross section for increased stiffness and grindability