There is provided an ultra high vacuum (UHV) compatible lead-through comprises (a) a housing, (b) a first space, within the housing, connected via a first port to a space outside the UHV-compatible lead through, (c) a second space, within the housing, connected via a second port to a closed system containing a polarized gas, (d) a movable component, separating the first space from the second space via an intermediate space, and (e) seals for limiting a penetration of volatile media from the first space into the second space. The lead through is particularly suited for use in the production of polarized gases, such as ³He.