These ball valves include a built in check valve to not only protect your regulator but also prevent gas or beer migrating from one keg to another. Should only be used with gas, not beer.
The manifolds we sell all come standard with 2, 4 or 6 output. These can be converted to 3, 5, or 7 output by simply unscrewing the 1/4 inch plug from the end of the manifold and inserting one of these 1/4 inch ball valves (see image to the left).
Please note that due to the check valve mechanism there is about a 2 psi pressure drop over these ball valves. You will need to set the pressure on the regulator about 2 psi higher than the desired pressure in the keg.