The invention relates to a device suitable for retrofitting in laid pipelines. Said device is intended to be able to be placed and fixed in place in the pipeline. Transport of the device to the installation location is intended to be performed using as little force as necessary, and the sealing element is to be displaced without contact and thus without wear. To this end, the device, in the interior of which a shut-off device (6) is disposed, is designed so that an offset, conically tapering region (10) is adjacent to a front cylindrical region (3) and is bounded by a stop collar (12) on which a connecting contour (7) for a coupling piece of a drive element is connected. A sliding piece (13) made of an expandable material is displaceably disposed in the axial direction on the conically tapering region (10), comprising a circumferential groove in which a spring-loaded clamping ring (15) is supported.