It's seriously PNEUMATIC...
My Great-Aunt Laura never had one of these! Of course, she was a school-teacher in a one-room school house, so I'm not surprised.
It's a rodless cylinder that moves waaaay smooth.
Yeah, this is over on the main project page as well, but we wanted to make sure that everybody knew about it because it's just so darn cool! (Or at least we think so)
BTW: This is the first of our ongoing series of 'In The Lab' videos showing how to use the SlingShot in the most awsomest ways.