Chirco offers a wide variety of VW Engine cases. The two main styles of VW engine cases we stock are the magnesium and the aluminum. We carry the stock case that is made of magnesium and is the latest version of the AS41. This case can be used as a stock case or can be modified for high performance and racing motors. Our aluminum case is a completely upgraded case with lots of features already included. Our aluminum case is fully CNC machined and is follows very strict guidelines.These cases are made of very strong high end aluminum giving you a little ease of mind on having a bad case. We also carry both the magnesium case and the aluminum case that come opened up for big bore pistons. If you are looking for more of a racing motor, the aluminum and magnesium cases that have already been opened up is the way to go. If you have questions in regards to which case would work best for you application, please let us know at 1-800-955-9795 and we will help get it taken care of for you.