And only used one with no problems. It worked fine with the Simon kit.
I ordered 4 and all 4 leaked.
These are decent low cost valves but I found they leaked CO2 in the closed position, even at very low pressures. After experiencing the dreaded suck-back of sanitizer into one of my fermentors during cold crashing, I purchased 4 of these so I could isolate the sanitizer jar from the fermentor and pressurize the line with CO2. Unfortunately when I tested the setup all of the valves had slow leaks of CO2 around the top and bottom of the stopcock when in the closed position. This was with the regulator set to less than 5 psi. Very small leaks, but enough to drain my CO2 tank over the course of 3 days of cold crashing. Interestingly, when I capped the line with the valve in the open position there was no leak, but they definitely leaked in the closed position where I needed a good seal. I found some other valves to do the job, unfortunately they were over 5X the cost of these....