You can see from the diagram that these struts have been designed to act as a single unit that includes an air bag. The struts have been designed around a very large dampener with the air bag replacing the coil spring.

The bags are make from a 2-ply structure to maintain excellent durability and strength under pressure. The bags have been tested in excess of 200PSI

Just like a performance coil-over, the bottom mounts can be unwound to extend the overall length of the strut to match the size of wheel fitted.