The X-7 Dimensionizer is the transport used by the Inspector to travel throughout space and time. It resembles the Red telephone boxes found in the United Kingdom. Despite its seemingly cramped design it can comfortably accommodate at least two people. Although the Inspector has used other vehicles such as the HMS Spacetime 12, he is most associated with the X-7 Dimensionizer and it has become a symbol of the show itself. Its first appearance on "Community" was in the Season Three episode "Biology 101".
The X-7 Dimensionizer is of course an homage to the Doctor's own time and space vehicle from Doctor Who, the TARDIS (Time And Relative Dimension In Space). Unlike the TARDIS, the X-7 is not bigger on the inside.