Smooth stop is a very good valve. Very efficient with air useage. I have had 2 ver. 1 and both leaked. If you clean them out, replace orings and oring lube, they are good to go. Geometry of servo to valve is a lil critical and the air in line needs to be "loose" to move around as the valve slides in and out. Smooth stop II with new plunger has addressed the problem of geometry but can rotate around due to the ball link linkage they use now. Still a nice valve and the rotation problem is easily addressed.