Just an idea for a printable piston I thought I'd jot down. It is designed to be printed without infill. The render is a cutaway, to show the bellows.I hope this little thing extends downward as it is inflated from the top. Probably not much of a stroke until it is tuned properly.I would like to use this thing to make a "pneumatic stepper motor" like my other thing: http://www.thingiverse.com/thing:33853Any feedback is welcome.Print with no infill.I have not printed this for I have no printer to do so (yet!) but would be very grateful to anyone who posts feedback on this quick print.