This Lexus LS430 Re-manufactured Air Spring Bag Strut Set will replace the original Rear Air Spring Bag Strut. What is an air spring bag strut, you say? An air spring bag strut is a strut that also has an air bag fitted over for a duel usage. The most common reason for an air strut failure is due to dry rotting of the air bag. This is something that happens over time, the air bag starts to deteriorate and causes leaks, when this happens the air bag can no longer hold air pressure. A leaking air bag can cause the strut it fits over to fail as well. The second factor of an air strut failure is the strut itself. The strut is pressurized with fluid, and if the strut begins to fail it will no longer have the same pressure to hold the vehicle. If this system begins to fail one visible sign will be that your vehicle will be lower than factory height. If Air Spring Bag Struts are not replaced on time it can cause Air Suspension Compressor Failure.