[Gmsh] Extrude 2D quadrilateral mesh and get hexahedrals

[Matteo Parsani]

Dear gmsh users and developers,
I have mesh a square cylinder in an unstructured way using only 
quadrilateral elements.
However, when I extrude it in 3D I get triangle, pyramids and hexahedrals. 
My goal is to only get hexahedral.

Could you please advice?

Please find in attachment the .geo file I am using

Thank you

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