I don't have photos right now ( and they look like the others) but I have a Slimline and a Minimalistica, both with the demo middle.
The Slimline is delrin on the section and the cap, while the M just has a Delrin cap.
If you are sensitive to slippery sections, I would stay away from the Delrin. I love the SL but find it is a little too slick. The M on the other hand, is clear right down to the section, and it is easier for me to write with. Both are great pens though.
Just my two cents.......