I am new to SolidWorks, but I have some experience with FreeCAD, so I have some understanding of parametric object modeling.  

I downloaded a bundle of SolidWorks files of an extruded aluminum bar provided by a vendor, from this page.  I'm going to cut this bar into parts of different lengths, so I wanted to create multiple part files from this starting point.

I opened the SLDPRT file provided.  I used Sketch > Smart Dimension and selected an edge at each end of the bar.  It shows that there's a Primary Value with the name TXD1@Scheme2 has a value of 1828.80mm (72").  But these fields are grayed out and I cannot change their values.

I also notice that there is a single Solid Body in the file called Imported1.  I would have expected to see a 2D shape and an extrusion operation applied to that 2D shape.  The Imported1 object appears to be monolithic: no shape, no extrusion.

The vendor also provided a SLDASM file.  I don't see the point because this is a single part, not an assembly. 

Can a hard-coded non-parametric object be embedded in a SolidWorks file?  Is that what I'm seeing here?  Is there any way for me to work backwards, extracting the 2D cross-section of the part so that I can apply the SolidWorks extrusion operation to it?

Thanks for your advice.