The vertical. is a simple wobblers that I built from what I could remember of plans that I saw when I was taking machine shop , it has a 3/8 bore and a 1/2 stroke and is single acting. The twin is one that I built one day just to see how fast I could build one! I finished it in 2hr.21min. from start to first run!! It is a single acting wobblers twin cylinder with .213 bores (I think I remember that right, I used the unthreaded part of long #12 bolts for the piston/rods, because it fit the brass tubing I had) and 3/8 stroke. The other is a double acting wobblers that I designed, it has a .875 bore and 1.250 stroke ,and it has a reversing valve built into it !