The invention relates to a device (1), especially a tube or a catheter, for at least partially introducing into a body passage, said device comprising a long outer envelope body (10), a long inner body (11) that is partially peripherally surrounded by the envelope body (10), and a device (12) by which means the possibility of a relative movement between the envelope body (10) and the inner body (11) is enabled or impeded in a targeted, controllable manner. According to the invention, the control device (12) is formed by the arrangement and embodiment of the envelope body (10) and the inner body (11) and comprises no additional mechanical means in the annular intermediate region (13) between said two bodies (10, 11). Preferably, the control device is embodied in such a way that it acts on the friction between the envelope body and the inner body (10, 11).