Today we will see a 2 years old MOC from Nico, which features a studless version of Sariel's pneumatic auto-valve.
In fact with his studeless design, Nico was able to build a dual auto-valve in a very compact solution.
You may see these auto-valves in action, from Nico's video below about the Bulldozer to which he developed this interesting solution.
Just in case you want to try it out, Nico has prepared also building instructions into a photo sequence, as already usual for some of his models (Click over the picture below, to get there).
You may found a lot more images from this model at Nico's BS folder, and read about this model in his own words (although in French) at Nico's page on MOCpages.