In DM, create a plane that is 0.4 mm offset in Z from the XY plane and use that to Slice all bodies. Create a plane 0.4 mm offset from the other end and slice. That way, all the elements between the slices will be very uniform.
I assume you need the 5 layers to assign different properties. If you don't then the mesh can be improved further.
Then with two mesh controls: Method Hex Dominant and Sizing on the end pieces, you get a fairly nice mesh. Is this for CFD or Structural? If it is CFD, then you will want some inflation on the fluid at the walls.
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