Abstract: A pneumatic valve assembly includes a valve body having an interior outer central passageway and an interior inner central cavity larger in diameter than the outer central passageway, a valve stem disposed within the outer central passageway and extending into the inner central cavity, a retainer member which supports the valve stem, and a flexible bendable annular seal flange attached about the valve stem held against an interior annular seal surface formed within the valve body between the central passageway and central cavity due to the support of the valve stem by the retainer member. Upon inflation, inward flow of pressurized air through an annular channel between the valve body and valve stem impinges on the annular seal flange, causing it to flex away from the annular seal surface and to permit inward flow of pressurized air.