13. Before you ask, no, we aren’t worried about chopping and splining a shaft. These axles are CNC induction heat treated to about 0.300-inch deep and the splines are about 0.060-inch deep. The CNC induction ensures a uniform depth and no hot spots. Factory shafts are heat treated to a depth of about 0.100-inch, so we’ve still got double the depth of any factory shaft.