An instrumentation delivery unit which supports hand-held dental instruments. In one example first and second housing members form a sealed chamber. When the members are separated, access is permitted to the interior of the chamber, e.g., for maintenance purposes. A first portal suitable for connection to a vacuum line provides a partial vacuum in the chamber, and second portals provide connection via second vacuum lines between the chamber and dental devices to operate the devices. The housing includes hand piece holders each of an initial diametric size for receiving hand pieces up to a maximum diametric dimension, with one of the hand piece holders formed along two adjoining ones of the housing members. The adjoining housing members secure inserts between one another to provide a second diametric size smaller than the initial diametric size to thereby selectably accommodate hand pieces having a smaller diametric dimensions.