The TRE Standard FSAE axle.  20 tooth 22mm OD spline to fit our 02002011 tripod as well as the 02002017 bolt-up CV joint and the 20 tooth FSAE CV spider.  

Cut these to the length you need and add snap ring grooves for joint retention.  Shafts can be cut down to ~2.25"-2.5" shorter than the unmodified length as there is ~2.5" of usable spline on each end. 

If cutting the groove yourself we recommend a good lathe and a carbide insert grooving tool such as this one.  Depending on your setup the speed can be between 100-300 rpm but the stiffness of your lathe, chuck, toolpost, etc will determine what works for you.  You can also use a Dremel type abrasive cutoff tool to cut the groove while the shaft turns slowly on a lathe or other rotary support.  It is very important not to cut the groove deeper than the root diameter of the splines or you will create a significant stress riser.

You can also have us cut the shafts to length and add the grooves if that works better for your team and tooling situation.  

We recommend using a piece of PVC tubing or wooden dowel to mockup the shaft length before cutting to confirm that everything works on the car before cutting steel.