Primo pro chromoly cranks the primo pro cranks feature a 3 pc design with heat treated chromoly crank arms that square off near the pedal bosses to prevent denting additionally they have wrap welded spindle and pedal bosses for strength a 22mm hollow heat treated chromoly spindle and hollow chromoly spindle bolts to help reduce weight without sacrificing strength rhdlhd features spindle 22mm hollow chromoly spindle bolts 15x1mm hollow flush mount x2 spindle splines 48 sprocket bolt 10