A valve for a pressurized container includes a valve housing having a central bore and a port in the for connection of a nozzle. Preferably, the valve has a unidirectional stepped valve housing. In the housing is a central bore that includes an upper portion, lower portion and a middle portion. The lower portion is narrower than the middle portion which in turn is narrower than the upper portion. The port is provided in the middle portion of said housing to facilitate connection of a nozzle to the valve. The valve has a t-stem with a lower end having a key-way and a cavity for receiving the upper portion of the valve seat. The valve seat provides the primary valve seal when the valve is closed. It has a lower portion that is shaped to provide the primary valve seal in cooperation with the valve housing. The upper portion of the valve seat has a geometry for engaging the t-stem to provide a locked assembly. The t-stem and valve seat assembly are located in the central bore and cooperate to position the valve seat for the primary valve seal. Preferably, a blocking element is provided in the lower portion of the central bore to prevent refilling of the container. An o-ring also preferably is provided to form a seal between the valve seat and the valve housing when the valve is in an open position.