A novel and improved inventive valve with a regulating function is provided that is capable of filling to higher fill pressures than previously attainable with conventional C-10 “on-off” valves. The valve contains a single flow passageway by which gas dispenses and enters the valve. A fill adapter is specially configured to engage the valve to allow filling at the higher pressures along the single flow passageway. The structure of the valve allows greater utilization of cylinder capacity; simplifies filling and dispensing with the single flow passageway; and allows for regulating gas pressure during delivery without increasing the overall size of the cylinder package.