A valve device regulates the air pressure in the space between a residual limb, or liner-covered limb, and a hard socket of an external prosthesis. A manually-controlled air-outlet and -inlet valve may optionally include an automatic one-way valve (or “expulsion” valve). The manually-controlled valve is opened and closed by twisting a handle, to open a two-way air passageway by slightly separating the handle and base portions, or by aligning bores in the handle and base portions. At least one stop surface limits the amount of relative rotation of the handle and base portions of the valve, so that the user need only rotate the handle a small amount, for example, less than 90 degrees, to affect opening or closing the valve.
