These forged stub axles will fit the stock IRS VW Thing.  They are also commonly used by off-roaders, rails, baja bugs, etc to convert the stock Type 1 rear axle to the larger diameter Type 2/4 100mm CV joints like those that came in the bus.  The CV's are not only stronger, they allow for more suspension travel that the stock Type 1 CV's allow.  For reference, Type 1 CV's allow up to 12 degrees of articulation.  Stock Type 2's allow for 17 degrees, and the Type 4 or off-road prepped Type 2's allow a full 22 degrees!  

These are also used for high powered street or strip cars due to the higher load on the drivetrain to prevent breakage.  As with any chromoly hardened axle component, you'll want to torque them properly with a torque wrench.  Don't use a pneumatic impact or a cheater bar!