I've never seen a sealed strut. It looks as if someone cut off the original strut tube, thus separating tube and spindle, then welded this "sealed strut" to it.

Hi Type4,

Welcome to the forum. The stut photos dont clearly show the top of the strut tube. Is there no large threaded retainer to hold in the insert?

The stut appears to have had a larger tube welded to the stub to allow the fittment of a larger diameter insert. This is a great mod to increase the volume of the insert to help with shock oil temps and foaming.

This tube, standard or modified like yours, is alway welded to the stub and therefore not removable. Only the insert is removable by undoing the threaded reatining nut/collar at the top of the strut tube.

Id be very suprised if the strut has been built so you cant get the insert out.