4000 series is for longer length to diameter ratios.  They may have dual actuation on both ends. Providing 4 independent expansion areas for a consistent deformation profile.

Typical 4000 series with standard ends and dual actuation on both ends

4000 series with both ends dual actuation and custom part features

4000 series with both ends single actuation and

two extended ends

Versitility....that is the Xpandrel Advantage.

How do I read Xpandrel part numbers

What materials can be used